Fill out the form. Because everybody has an opinion, and a best way to do things. Here, we will let the appearance of empirical data show us wondrous things, or perhaps nothing at all. I thought about throwing FTP on there as a variable, but I dunno how many people know theirs.

Chain brand: Shimano Ultegra, CN-6701
Speeds: 10 speed
Surface: road
Bike + rider weight: 220lbs
Lubricant: Muc-Off Team Sky Hydrodynamic
Lube interval in miles: 500
Remove chain to clean/wash? No, just wipe off outside chain when needed
If yes, how often: N/A
Average chain life in miles: 3,000


Here's a blank for y'all to cut and paste.

Chain brand:
Speeds:
Surface:
Bike + rider weight:
Lubricant:
Lube interval in miles:
Remove chain to clean/wash? Y/N
If yes, how often:
Average chain life in miles:

Chain brand: KMC
Speeds: 10
Surface: Road
Bike + rider weight: 200 lbs
Lubricant: Mineral Spirits + Oil
Lube interval in miles: Every now & then
Remove chain to clean/wash? Y/N ...No
If yes, how often:
Average chain life in miles: No idea

Chain brand: KMC X10SL
Speeds: 10
Surface: road
Bike + rider weight: 165
Lubricant: Chain-L
Lube interval in miles: 750
Remove chain to clean/wash? hell no
If yes, how often: never
Average chain life in miles: 6-8,000

You left out the "I've done xx for yy years and it works for me" bit.

Chain brand: Dunno, whatever came with the bike
Speeds: Mostly slow
Surface: Mix of gritty rural asphalt and gravel
Bike + rider weight: 195
Lubricant: Park CL-1
Lube interval in miles: 100-300, depends on conditions
Remove chain to clean/wash? Y/N: Nope, but occasionally remove rear wheel to clean sprockets
If yes, how often: Once or twice a month
Average chain life in miles: Dunno, replaced one chain in five years on last bike -- I'd guesstimate I rode more than 20,000 miles in that time, so that's pretty good life from two chains. This one is going on a year. Maybe 1,500 miles so far. My monthly average has gradually increased from 100 to 300-400 miles since I resumed riding last August.

I will admit that I don't know the lifetime of my chains, and that those who do, might not be representative of mainstream cyclists.

Average chain life in miles: Unknown

I say Unknown because I've replaced roughly three chains in my life due to measured "stretch." In all other cases, I've replaced chains because they were rusted out and seized up (neglect, not wear-out), or because I changed the entire drive train. And I don't count miles.

Chain brand: Suntour Ultra 6
Speeds: 6
Surface: Road
Bike + rider weight: 149 lbs
Lubricant: Tri-Flow
Lube interval in miles: ...1-2x/month
Remove chain to clean/wash? Y/N - No
If yes, how often: N/A
Average chain life in miles: Who knows...

Chain brand: SRAM PC 850
Speeds: 8 speed
Surface: Mostly Road, a little packed limestone
Bike + rider weight: 190 lbs.
Lubricant: White Lighting Epic Lube
Lube interval in miles: 200-300
Remove chain to clean/wash? No, just wipe off outside chain when needed
If yes, how often: N/A
Average chain life in miles: 3,000 - 5,000

Chain brand: Campagnolo Record 10
Speeds: 10
Surface: Road (asphalt); varied terrain--flats and well as lots of climbing
Bike + rider weight: 160 pounds
Lubricant: White Lightning
Lube interval in miles: Chain wiped off and lubricant applied before every ride
Remove chain to clean/wash? No
If yes, how often:
Average chain life in miles: 10K miles (I have always been an easy keeper on chains: proper shifting, I guess; light weight)

I just checked my Amazon history, 9 chains purchased (including on a new bike, plus one in a local bike shop) since July 2012
Every 6-7 months a new chain, so I'm estimating the miles per chain from that

Chain brand: SRAM (6) or KMC (2) 1-spd (1)
Speeds: 8
Surface: paved
Bike + rider weight: 175 lb regular ride up to 200 lb commuting
Lubricant: varied, mostly white lightning
Lube interval in miles: 100-200
Remove chain to clean/wash? Y/N NO
If yes, how often: n/a
Average chain life in miles: 2500-3500 miles

Chain brand: Mostly SRAM. A couple of KMC X9EPT Eco Proteq for winter use. One stupid Shimano 10 speed
Speeds: 9 and 10 (1)
Surface: You name it, I ride it. Dirt, paved, rocks, sand, floods, locusts, plagues of Egypt, etc.
Bike + rider weight: Um. North of what I should be but my bikes are fairly light. Let's just say solidly clyde. Bikes range from a portly 28 lb to a rather svelte 20 lb...but portly compared to carbon fiber norms
Lubricant: White Lightning Clean Ride
Lube interval in miles: 400 to 600 miles...White Lightning is very wrong on their application interval. But they are trying to sell lubricant.
Remove chain to clean/wash? No but that's because I don't clean it except for on initial installation
If yes, how often: Once.
Average chain life in miles: Estimate about 3000 miles. Actual measurement of one chain: 3500.

Chain brand:
Speeds:
Surface:
Bike + rider weight: Firmly in Clydesdale territory
Lubricant: Boeshield T-9 ("dry" bike) or 50/50 90 wt. oil and OMS ("rain" bike)
Lube interval in miles: whenever it needs it (typically 300-800 miles)
Remove chain to clean/wash? Nope
If yes, how often:
Average chain life in miles: 2,247 miles. +/- 500 miles.

What's FTP?

Chain brand: Shimano Ultegra, SRAM
Speeds: 9 speed double, 11 speed double
Surface: asphalt
Bike + rider weight: 21# + me, 16-17# + me
Lubricant: Triflow, White Lightening Clean Ride, Rock N Roll Gold
Lube interval in miles: 30-150 depending on the weather
Remove chain to clean/wash? Y/N: N
If yes, how often: N/A
Average chain life in miles: 2000-3000

I'll play:

Chain brand: SRAM PC-1071
Speeds: 10 speed
Surface: Road
Bike + rider weight: 167 pounds
Lubricant: ProGold Pro Link in a Finish Line No Drip Applicator.
Lube interval in miles: 200-300 miles or weekly.
Remove chain to clean/wash? Y/N No
If yes, how often:
Average chain life in miles: 2,000-3,000 miles

Chain brand: Shimano CN-HG92
Speeds: 9
Surface: Road
Bike + rider weight: 185
Lubricant: WD40 Dry Lube PTFE
Lube interval in miles: 250
Remove chain to clean/wash? N
If yes, how often:
Average chain life in miles: 3200

Chain brand: Whipperman Full Bush 3/8:
Speeds: IGH 3 by 2 [Rohloff 14]
Surface:in Town .. paved.
Bike + rider weight: Brompton M3L [Bike Friday Pocket Llama]_ 210#
Lubricant:Triflow
Lube interval in miles: Random
Remove chain to clean/wash? _ N
If yes, how often:
Average chain life in miles: don't bother with computer to track them

Chain brand: KMC
Speeds: 9
Surface: Road
Bike + rider weight: 230
Lubricant: Paraffin, White Lightning
Lube interval in miles: 100 miles, wipe & WL (one minute of maintenance every 3 rides)
Remove chain to clean/wash? Yes, too easy not to, no black grime, no dirty hands.
If yes, how often: 500 miles (rotate 2 chains, soak for a day or two to clean, 45 minutes for the hot wax...just have to monitor the pot on the stove)
Average chain life in miles: 2,000 miles ea on current pair and no measurable increase along entire length ...first to last link right on the inch marks.

Chain brand: SRAM PC-1170
Speeds: 11 speed
Surface: crushed limestone and dirt trails (mostly), gravel, pavement
Bike + rider weight: me (clyde + 20 lbs bike)
Lubricant: pro-link gold
Lube interval in miles: 30-100 mi
Remove chain to clean/wash? Y
If yes, how often: every ride or every other (limestone is awful)
Average chain life in miles: Don't know yet


Chain brand: Ultegra CN-6701
Speeds: 10 speed
Surface: crushed limestone and dirt trails (mostly), gravel, pavement
Bike + rider weight: me (clyde + 21.5 lbs bike)
Lubricant: pro-link gold
Lube interval in miles: 30-100 mi
Remove chain to clean/wash? Y
If yes, how often: every ride or every other (limestone is awful)
Average chain life in miles: 3000+

Chain brand: KMC
Speeds: 9
Surface: Pavement
Bike + rider weight: 155
Lubricant: GM EOS
Lube interval in miles: ~200
Remove chain to clean/wash? N
If yes, how often:
Average chain life in miles: ~ 6,000