You've got a long way to go before you wear that machine out.
I know of a 2015
HST with over 1100 hours, and a 3015HST with 900. Also, a friend of mine has a Cub Cadet 7265 (exact same tractor you have, only yellow) with over 2000 hours. That tractor starts and runs like the day he got it. It doesn't leak a drop of oil either. Just keep your fluids and filters changed. I think most people would say you could reasonably expect at least a couple thousand hours out of a compact tractor.
As far as the cracking blocks, and related issues, Most of the posts on
TBN say that its very rare, and it's usualy attributed to loose loader bracket and subframe bolts. I was under the impression that it was more of an issue with the earlier Cub Cadet models, (I could be wrong). Just check them to make sure they're tight every time you do a PM.
As far as who makes the transmission... Couldn't tell you, but I'd be interested to find out myself. I'd bet Eaton has something to do with it.