I get 2-3 yrs out of micron extra in Puget sound, as did the previous owner.
Now with that in mind, I will sorta echo what mainesail is saying in that i have a pretty good build up of paint
on the bottom after 25 yrs, and it is looking close to needing a complete grind down to gelcoat.
Generally speaking tho, one can paint
over an ablative with a different type or brand ablative paint
. There are some exceptions, look at the manufactures suggestions as to whether you can or can not paint
over what you have with out doing more.
I do get some slime with my bottom, and also as mainsail mentions, it takes 5-6 knots before things seem to get removed. I was out friday, hit 5-6 knots for the first time since Oct for any length of time, and the bottom was a bit cleaner on the return than the previous trips out where we were barely over 4 knots. I'm toying with a hard paint, as we can in-water clean hard paints here in Puget Sound, but ablatives it is illegal to majorly frowned upon.