Replace or repair skylights?
Is he sure it is the seals? Sounds like NO.
It is reasonable IF you are sure it is the seals that are the problem.
It could be that the flashing is the problem, when the snow was deep enough to cover the top of flashing it may have leaked in at that point. Without knowing the exact problem then it is a gamble weather or not repairing the seals is a reasonable coarse of action.