Dakota drive shaft-with static drop

My friends buddy just turned 16 and bought a 6-8 lowering kit for his dakota, and i was talking to a guy that owns a shop, and he said you have to shorten the driveshaft when going more than 3 inches in the rear, i was just wondering if this was true. and if so how far? he told me 2 inches and i thought that was little much.

mine was lowered 4" in the rear before and my shaft broke and there was another guy on here ask me about it cause he's went through two of them.i dont know why it broke but it must be a pretty slim chance but thats just my luck. i bought one that was 1 1/2 shorter and i've had no problems since. i think it depends on pinion angle cause the blocks i had sucked and my angle was off.

mine is monster notched and 3 link with stock driveshaft no probs what so ever

I DIDNT HAVE ANY TROUBLE OUT OF MINE EITHER.