We burned out one 775 Pro motor on our drive during the regular season. This was at our first district event (Southfield) and was caused by a programming issue we had in a match that caused the robot to drive into a wall for more then half the match.
We had one of our 550 steering motors burn out at our third district event (Windsor), as something caused the VP it powers to jam (we think due to poor initial assembly).
Our drive performed poorly at our second district event (Milford) due to an MA3 encoder failure on the back-left module. We speculate this was due to ESD, but really have no proof of that, just deductive reasoning that nothing else appeared wrong with any wires or anything mechanically involved. We would likely switch to using Mag encoders or some other solution in the future to avoid using the MA3, which is more exposed to potential issues like that.
Those were the only failures in the competition season. We have had three drive motors fail at off-season events this year, however all had the fans torn apart on the inside. We have at least one occurrence that we think we can trace back to a cube landing right on top of the motor and likely slamming the wire leads further into the casing, interfering and imploding the fans. So we think the cause of these motor failures in the off-season has been due to poor design on our part of having the vertical mounted motors so exposed to contact with things.
If we were to run this or a similar swerve in the future, we would definitely find a way to more soundly protect the top of the motor. In a skid steer drive, this generally would not be an issue at all.
I will say that overall at competitions, even going through playoffs, we never really saw our drive motors heat up excessively. The steering motors got way hotter (we will be tinkering with ratios for that if we do it again). The only times our drive motors really got hot was after a lot of practice cycles at the shop.
I know that these motors will degrade over time and use, other teams have tried to post their findings and experiences. We have not done much testing to quantify this at all as of yet.
For those curious, the drive was 6x 775 Pros total single speed, with a 12:100 32DP stage, a 16:26 20DP stage, and a 15:15 bevel gear stage. Overall reduction of 13.54:1, and a theoretical free speed of 18.1fps with 3" colson wheels.
We would likely run a little slower theoretical free speed in the future, but of course this depends on the game.