if they are replacing the belt that often, you are having problems with
1) the clutch, its junk and hard to make it run properly once some joe-schmo at a dealership has touched it
2) possibly driving style to be leading to multiple blown belts in such a short period of time.
the clutch is bad from the factory, they suck you can get a good one and never have a problem or be like one of the other hundreds that have had it blow apart and blow belts left and right. if they replace the clutch and you are still blowing belts then you need to look at your driving style, what are you doing when the belts keep letting go? try and find a pattern of what you are doing when each belt lets go, and then try to limit your exposure to doing that particular event such as top speeds for long periods of time on pavement, back to back long uphill climbs, holding the brake and the gas at the same time on hills ect. if your dealer completely replaced the drive clutches and you are still having problems you are probably blowing the belts yourself.
if your dealer is going to replace your clutches with something out of an 800, he is WAAAYYYY off base. the maverick trans and diffs are built bigger and stronger, plus the 800 trans has a different belt alignment. he is going to get you in all sorts of messed up situation if he replaces anything from your machine with can-am 800 parts. if you cant figure that its anything you're doing wrong i may think about changing dealers