What are you worried about replacing? You'll be able to get brake pads, wheels, etc. Sourcing replacement levers or derailleurs could get tricky down the line, but I'm not familiar with the life expectancy of these items. But yes, you could always go mechanical, with either an older groupset or with a lower-tier groupset.
If the bike does what you want it to do (for the foreseeable future) and the value is right, go for it.