In my experience drive oil is the critical factor Without getting into a pissing match about what oil is better I will simply say good oil is fresh oil. Change it every 10-15 hours on the drives with bigger motors and you will be ok. If you have over the rated hp for the drive I like to inspect them at the 50 hour mark. It shouldn't be a problem keeping an xr style drive alive with under 1000 hp between the 50 hour inspections assuming the oil is kept clean and fresh.