There is very little difference between so-called multi-season epoxy
ablative and the cheaper single-season equivalent in terms of efficacy after a prolonged dry period. Some of the paint formulators will tell you and advertise drastic loss of efficacy if paint is allowed to dry and in so doing try to influence folks to buy the more expensive paint claimed to have no such loss after being dry.
Two things to consider:
1. Being a chem engineer
, I too wondered about these claims and spoke with my colleagues at some nameless formulators about the differences. Essentially there are none which affect efficacy after dried. This isn't to say there are no differences, just none which would support their advertising in my opinion so being a typical cheap
boater, I experimented with my own boat.
2. Most recently, our boat in RI has been out of the water for over a year after having been painted by a single
season ablative marketed by WM 2 years ago. After having little use after being re-launched, there is no extraordinary buildup of marine
growth more so than that experienced after applying the same paint immediately prior to launch in past years.
Some case can be made for certain so-called copolymer ablatives but the components of these paints differ in ways totally unrelated to how drying affects efficacy in my experience.
It is always difficult to generalize when it comes to bottom paint because of so many variables such as frequency of use of the boat, water and weather
conditions, ambient temp variations, etc... but taking all that either into account or knowing conditions were static in my case, we found no difference.