I do a twice a year check on all roof jacks and fixtures and all lap sealant.
The sealant on my '97 5er's skylite pulled up for about 10" on one side in '05. I pulled all that would come off and added Dicor self leveling to that spot.
I also added a bit of Dicor to a few small hairline cracks in the sealant.
The unit has never leaked other than hail cracking the same skylite 6 years ago. I replaced it with a unbreakable one made of Lexan.
I installed the new one as the factory with butyl tape 1st and then Dicor over the edges and screw heads.
There are other good sealant brand on the market that work just as good as Dicor.