I'm wondering how many miles you should be getting out of a Dura Ace 9000 11 speed cassette. The reason I'm asking is that I just replaced the chain and started to get some slippage on the low end of the cassette while in the small chainring. I'm running DA Di2 and it really doesn't require much adjustment but I checked it out anyway.
I'm thinking it might be the cassette which has a little over 3500 miles on it. Does that sound like it's in the ballpark?

That's less mileage than my experience with DA cassettes, but I ride in an area that is easy on component wear.

3,000 sounds low.
Ultegra Steel seems about 5-7 chains.
DA about 4-5 chains
Alloy about 2-3 chains.

+1.

On the other hand, I have a NOS aluminum Campagnolo freewheel that might last forever.

In all seriousness the chain measure is a better one. Chains for some riders last 2-3 times as long as for other riders. That is based on dirt, lube and power. Which is the same stuff that wears out a cassette. I've had 4 tandems and the ratio was about the same on them - although everything wore faster.

And - FWIW - larger cogs wear things less. So a 13T-28T with big rings is less wear than an 11T-28t with smaller rings - that is if you use the 11-12T.

Then if you cross chain a lot, that wears things.

Too much lube collects dust.
Too little lube increases wear.

I thought the mileage was on the low side myself especially since I got almost 3000 on the chain. I'm on the anal side when it comes to maintenance so the drive chain is clean and lubed. I don't ride this bike in crappy weather so really it should last longer.
I put the new cassette on so I'll give it a go tomorrow and see if that takes care of it. I have a feeling it's something else but we shall see.

The answer totally depends on how much chain stretch you allowed before you changed the chain. If you kept the chain on too long, the wear on the cassette was greater and the misfit to the new unstretched chain will be greater.

this. if the chain skips on the first chain replacement, you let the chain stretch too far before replacing it.

Yep, probably this. One other thing to check out is the links where the new chain is joined.

10000 miles on mine and 2 chains doing well I expect many more. If

5000 miles/chain? How frequently do you measure change stretch and how much stretch do you allow before you change chains?

It's possible I allowed too much chain stretch before I replaced it. I had 3400 miles on the chain and according to the chain checker stretch was just a bit beyond .75
Then again after seeing deacon mark's numbers maybe not.
I checked the link where I made the connection and that seems to be ok.

Yes you waited too long. The good news is that skip will be gone in two weeks. Replace the cassette with the next chain or you will be replacing chain rings.

The symptoms suggest you waited too long, but I would have thought that 0.75 should be the right time for replacement. 0.5 would be very conservative.

I am my own mechanic do all my own work. I live in the flatlands that has a bit to do with chainlife and I do not normally ride in the rain so that has something to do with it. But the one thing also that helps is I keep the chain clean and well lubed. I use a wipperman connex so I can simply take chain off and wipe it down with OMS then re-lube. I am not anal or spend huge amounts of time with this but I easily get 5-6000 miles on a chain. Frankly I could get more I do not change them when they are at any specific stretch. I do not use chain checking tools, I use a good steel ruler line up pins. My present chain on the motobecane has 6000 miles and no real stretch less than 1/32 of an inch. Shifts perfect but I will probably change in in about 500 miles chains are not that expenses.

I agree. And I have NEVER replaced at 0.5.

KMC, Shimano, SRAM, Park all recommend replacing 11-speed chains at 0.5, 10-speed and under at 0.75.

My last 11-speed KMC chain was at 0.5 after 1,800 miles.

That's interesting to know. My only 11 speed bike is new and only has 1k miles, so now I am forewarned.

I generally change the chain at 0.75 and considered 0.50 half life and check it every couple of weeks. I may have not checked it for the last month because I was startled when I did check it and it was slightly more than 0.75. So you could say I blew it and waited too long.
In any event it must have been the cassette because I replaced it last night and when I rode today shifting was crisp and quiet so problem solved.

What's your average cadence?
~3500 miles sounds low, unless that includes >500K ft of climbing.

I'm not a spinner but I'm not a masher either. Generally between 75 and 85. It's something I'm always trying to work on.

Also check for sticky links which will cause chain suck and sometimes skipping. A new chain sometimes will have a sticky link or two that need lube and some working in. They shouldn't. But sometimes do.

Also, derailleur alignment can play a role in ghost shifting and a froggy chain. Sometimes a new chain is more finicky than an older one, but shifting problems with the old chain usually mean it's done for too.

If the sprockets are somewhat worn, the first call from everyone is "replace them (rings and cassette)". But in reality, "somewhat" worn sprockets will cause a chain to stretch faster at first (until the chain is set in) and then they will still work fine. Eventually the chain will be stretched past the limits of the worn sprockets and it will start to misbehave, usually quicker than on good sprockets. But chains are $20-40, while chainrings and cassettes are much more.

On my Red 10 drive train, which has maybe 12,000 miles on, it I see evidence that it is near end of life. I get notchy shifting with new chains, and poor shifting when the chain gets stretched. But even still, my latest chain was put on in July and has over 3000 miles on it (only caught in the rain once, and lubed the next day). So I'll probably just replace the chain one more time and keep on riding.

.....Also, derailleur alignment can play a role in ghost shifting and a froggy chain.....

We have a winner. I thought I had the problem solved with the new cassette but yesterday I was climbing a hill and when I jumped out of the saddle to crest the hill in the 34 x 26 and the chain skipped again. So now I'm thinking it could be a bent derailleur hanger. Checked it out and sure enough it was bent. Knucklehead that I am while attempting to straighten it out with the Park Derailleur hanger alignment gauge I managed to overdo it and break the hanger. Fortunately the LBS had it in stock so I replaced it went for a ride and really worked the upper end of the cassette in the small chainring and finally it's shifting as it should.
I'm glad I saved the old cassette since it most likely still has about 3k miles in it.