I think the more important quality is the attack envelop of the note -rather than the sustain, though they are linked.
I used to have a Warwick streamer, lovely thing, and like a lot of well built thru necks could sustain for hours. But when I got it it had active MEC pickups the attack was so quick it could sound like a machine gun, it sounded like it wasn't sustaining at all... based on the attack of the note.
When I put passive Bartolini in it the attack was more subdued and it sounded like it had a lot more sustain... even though it really didn't.