A friend recently purchased a 1988(I think) Cherokee, 6in lift, a few other mods. Anyway, after rock crawling for about 4-5 hrs the first day he had it, when we got back on the highway to go home, we noticed the rear of the truck was sagging badly. We are pretty sure the rear springs just fatigued, and he is gonna get spring blocks to lift them up(that hopefully will help stop the rubbing that was happening also).

Are the springs on these jeeps that weak, or were they just old and that kind of terrain just killed them??

Had the same problem on '89, just went to air shoocks to by-pass the weak springs.

A friend recently purchased a 1988(I think) Cherokee, 6in lift, a few other mods. Anyway, after rock crawling for about 4-5 hrs the first day he had it, when we got back on the highway to go home, we noticed the rear of the truck was sagging badly. We are pretty sure the rear springs just fatigued, and he is gonna get spring blocks to lift them up(that hopefully will help stop the rubbing that was happening also).

Are the springs on these jeeps that weak, or were they just old and that kind of terrain just killed them??
It depends on how the thing was lifted. It's possible the springs were weak and the off roading over extended them (bent them too much).

Lift blocks present their own problems, and the springs may just sag further. I would suggest a new aftermarket spring pack, whatever is appropriate to match the 6 inch lift.