Hi rmtaylor. Before Stuart pops in with his answer, I wanted to ask WHO started your husband's Buttonholes? If he started them himself, he shouldn't have any trouble finding them again. But, what often happens in dialysis clinics (perhaps due to control issues among the nursing staff, fear of lawsuits, or some other reason) is that the staff insist on starting Buttonholes for people. The problem is, the angle that a nurse would use is almost certainly different than the one a self-cannulator would choose. This can make it very difficult to hit the mark, as it were.
Needle length can also be important--especially for a zigzaggy fistula. A shorter needle will give him more chances, and there's really no need for it to be long.