I've worn out another 10sp cassette and chain on my main commuter, a Trek 7.7FX. I'm getting tired of how often I need to replace these parts. Chains every 4 months, cassettes every 8. Since I need a new chain and cassette anyway, I'm thinking of replacing the shifters too and just going 9 speed. My shifters are Shimano R770s with about 15000 miles on them, so they have some wear. I could get 3x9 R440s, which (I think) should be compatible with my R773 FD.

Has anyone here ever downgraded from 10sp to 9 on their commuters? If so, did you find it increased the lifespan of your cassette and chain? The long term savings of buying 9sp parts instead of 10 is attractive, but I'd have to say my main motivation is more durability and less maintenance. I welcome anyone's thoughts on the conversion.