It's amazing to see so many threads pop up concerning chain cleaning - must be a lot of concern/confusion about this subject.
Having participated in several of these LONG threads, myself, I have come to the conclusion that cleaning/lubing basically serves a "cosmetic" purpose only - not just appearance, but the lube keeps the chain quiet, also (I can't stand riding with a chirpy chain - has happened to me once or twice when I thought I had it well lubed, but turns out my effort was not sufficient).
As for wear, I am convinced that, if you put miles on the bike, the chain will pretty much wear no matter if you lube conscientiously or not. I have done no blind tests, but, in my own use, the last chain that I replaced was shot after 1500 miles - really stretched so that it ruined a couple of cogs (the ones I obviously use most) on my rear wheel. I replaced the chain and all the cogs (joy in Millville again). Now, the subject chain received the best care I could possibly offer - regular cleaning, plenty of lube at all times - clean cogs/chain rings at all times, also. Yet, it wore out after just 1500 miles.
I was riding hard (lots of climbing in longer gears) - I don't know if that makes a difference - but it makes sense to me that it might make a difference. I'm guessing that if you ride mostly flat/rolling terrain that the chain may last longer. Perhaps if you rode mostly granny gears uphill, that could possibly put less strain on the chain - I don't know, though. Just guessing.
I have resigned myself to more regular chain replacement to prolong the life of my cogs - I'm guessing that cogs should run a really long time if the chain in use is always in great condition - maybe I'm wrong on that score, as well.
For me, the bottom line is that, if I want to continue riding a lot and riding hard, then, I will have to also live with the reality that the drive train of my bike will need regular upkeep beyond simple cleaning and lubing.
I would love to hear input from others on this aspect of chain/bike maintenance.
As to Sprint75's question regarding use of WD40, it is a penetrating oil, designed really to degunk nuts/bolts that are stuck and won't turn. It's not designed so much for lubing. That's why you see folks on this forum using it in the cleaning stage, but then using some other lube in the final step.
I have Crankbrothers Candi-TI pedals on my C'dale. Once while out riding, they developed a really annoying squeak. The only lube I could find at that late hour was some WD40. I assumed (correctly, I think) that the squeak was caused more by the rubbing of the plastic (or whatever) washers on the inside of the pedals than the inner bearings (I guess that's what's in there, have never disassembled them to have a look). I'd spray it on, ride five miles or so and have to stop to reapply.
BTW (and this, I know, is a little OT), I love the Crankbrothers setup where you just screw in the little adapter and pump in your lube. My LBS guy sold me some lube from a can that he uses on these pedals instead of grease - I've been using it for a while with no complaints from the pedals - curious to hear comments on this also).
Some forum members will probably be annoyed at yet another lubing thread, but, I love reading them - seems like each thread, at some point, has some little new point for me to pick-up.
Caruso