The shaker grates should just about last a lifetime.. as long as the ashpan is not allowed to get so full that the ashes touch the bottom of the grates, this allows the grates to overheat and warp.. if the bottom of the grates are not touching ash, they will last decades..
Firebrick ocasionally crack, but they cost only a dollar or two each, and a crack does not make the brick bad,, it will still function.. many cracked bricks stay in stoves for years untill the owners get around to replacing them.
The gaskets on the doors need replacing every year or two,, this is a simple operation. The chimney flue pipes need cleaning every year, and depending on how much horzontal flue you have, maybe a cleaning every month or so during the burning season.. take a look at the 'venting and chimney' forum for threads on this subject.
All in all the stoves don't need a lot of upkeep.