Really good question, though- I checked a few guys (Gordie Howe, Yzerman, Bobby Orr), and you see 2-3 year streaks of improvement, but 7? Whoever it is, that's a pretty amazing feat.
I only have a vague memory of leeman .
i kinda think he may have had some off ice problem(either enjoying himself with a teammate's wife or his wife with getting it on with one of his teammates........if you get my drift).