There's nothing wrong with a Schumacher diff, and certainly don't need rebuilding after every meeting. I generally do 10-15 meetings worth of running on a diff before rebuilding.
An important part to any ball diff build is to run it in and set it properly. There's a good guide on it here:
http://www.rctech.net/forum/electric...er-clutch.html
If you need any more info on building/setting/running a Schumacher diff feel free to email me at Tom at racing-cars.com and I'll help you out.