Fox Shocks... How often should they be rebuilt?

Good chance that your 96 ZRT needs to have the shocks rebuilt. Depends on how many miles you put on and what type of riding you do. Most guys rebuild once a year or every other year depending on how hard they are on the sled.
Cost varies call around. I think it should cost around $30-$35 per shock. But it is worth it you will notice a definite difference in the ride and handling.

Ideally, you should rebuild them every season, but very few people do. I have heard every 1000 mi. for Fox Shocks depending on how hard you beat on them. Otherwise, by the 2000 mile mark i would recommend it. It makes a huge difference when you really start jumping and landing hard. I get mine done on my 440 if i feel them start to fade. Bad seals will leak. Dirt can also pit the shaft and allow moisture inside, and the Nitrogen charge can escape creating a crappy ride. Polaris dealer charges me $20 per shock, unless some of the seals are worn or cracked. Clicker-type shocks and external reservior can cost more to have done.

I think that shock life has alot to do with how clean you keep your sled and how much trailering you do with it exposed to salt and dirt. I would rebuild every year...why not it's cheap performance?

2002 Arctic Cat ZR 800 EFI
1993 Polaris Storm 750
Piped and Clutched

rumor has it that fox shox should be rebuilt every two years, that is if you have no problems before hand, mine on my xlt are a year old, so i plan on rebuilding them maybe next summer.