Balls mate ...... of and lube of course
It's all to do with having well lubed balls!
The diff in my DB2 is still perfect after 5 meetings without being touched, not getting a hammering at all.
I did use fresh diff plates, sanded from new, fresh BRG100 thrust race, X-gear lubes and finally RudeBits carbide diff balls.
Trust me, use the RudeBits carbide balls with Kyosho/Xgear stuff everywhere else and you'll be golden.