You really need to find out what the existing paint is. Without that information, one is really just guessing.
Some bottom paints (but not many) can be left unlaunched for quite awhile and still be effective.
As for repainting - again you need to know what is already there as many bottom paints are not compatabile without a barrier coat being applied first.
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence