Cardas Phono Cartridge

A while back I purchased a Rega P9 table that came with a Cardas Ruby cartridge.  I didn't know how much use was on the cartridge but it sounds great and is a much nicer cartridge then any I had used in the past.  This is really an expensive cartridge and I'm wondering how to know when it should be repaired?  Where do you send such a cartridge to be repaired once it is worn?  Thanks for any input that anyone can offer on this.  I know that it can be rebuilt by Sound Smith but that's not quite the same is repaired by Benz and I saw they don't offer that service any more.