I split my mileage up between three bikes, so it will be a long time before I know how long a cassette lasts. As for the chains, I'm not seeing a major difference between 10 and 11 speed, but I know the 11 can't last quite as long. The greatest mileage I ever got from the wider 6.1mm 10 speed chain was 6,000 miles. The 5.9 would get less and the 5.5 less again.
I'm relatively optimistic that I'll have no problem getting 4,000 miles from an 11 speed chain and the life of 3-4 chains from a cassette, as long as I use those chains in a rotation, so chain skip is never an issue. Then the life ends whenever I finally decide to toss all the chains and the cassette with it. Long before that time, there will be one or two cogs worn enough that they would skip if a new chain was installed.
The definition of "chain life" is somewhat elusive. A chain checker always exaggerates the wear and leads many people to toss half-worn chains. I'll use mine until the roller spacing is at least .240 inch, but each chain will be on and off the cassette several times before that much roller wear occurs. I still don't expect the elongation to exceed .5% - properly measured with a precision ruler.
About that record cassette, Danton. I only pay about $100 USD for a Chorus cassette. A Record model is more that twice that. http://www.ribblecycles.co.uk/pp/road-t ... -Road/CASS
Whether the larger Ti cogs wear out first depends on where you ride. I do a lot of climbing, so the Ti cogs would be some of my most-used. Despite being larger, they will be the first to go and last half as long. I'd pay at least 4 times as much to use Record cassettes.