RV Repair: rbw electric leveling jacks, fifth wheel trailer, worm gear

Question
I have a 1999 prowler fifth wheel trailer with rbw jacks I have replaced the gears on both sides,plus the the big nut on the worm gear on one side once and have just lost it a second time.Is this a common problem with rbw jacks or is there some way that I can keep this from happening again?

Answer
Walt,
    Usually the thing that tears up these jacks is not having the weight evenly on both legs or just too much weight.  I don't have any lines of RV's that use this brand so I really don't know if it's a common problem or not.  I don't have a lot of problems with the Atwood jacks that all my trailers use.

Darren