I haven't read any post with anyone having to change there ball joints after installing the leveling kit along with the 6" or 8" lifts. It put's more stress on your ball joints causing them to wear faster, but exactly how much faster? How many miles have you put on your truck before the ball joints have gone out? If you have just a leveling kit then the question is for you also.

 

Too many variables and there's no rule book on this anyways. Your truck/situation will be different. Bottom line, drive it and enjoy it until it "needs" them. Don't try to outthink them and change them anyways or just because. Get your money's worth out of these first.

Similar story...tons of guys on here with lower ball joints going out at all variables of mileage (30-50k) with lift kits on my body truck. Well, 109,913 today and still running the original lower ball joints. Everything else on the front end has gone bad and been replaced, but by lowers are holding strong. And I'm not going to replace them until they go. FWIW, my original uppers made it about 25-30k after the lift install before they went out. Everything else (tie rod ends, etc) made to 100,000.