Aside from environmental issues, the type of bottom paint
you use should depend on how you use and maintain your boat.
Hard bottom paints
last longer than ablatives, but, after you have applied them for a period of years, they build up a thick coat of old paint
that eventually starts to crack and peel. When that happens, you need to consider stripping all the old paint
off the bottom and start over again. If you do a good job of sanding it between each coat, and if you apply each coat properly, you might be able to go nearly 20 years before you strip it. If not, you might have to strip it much sooner.
Realistically, I think ablative paints are only good for one year. If you want a bottom paint that will last longer, you need a hard finish paint. Over the long term, ablative paints will save you a lot of labor maintaining the boat.
If you keep your boat on the hard during the off-season, then you can give your bottom a light sanding in the spring, apply a coat or two of ablative paint, and you'll be good for the season. If you keep the boat in the water for 2-3 seasons, then you have to use a hard finish paint.
Unless you're a serious racer, the bottom only needs to be stripped when it accumulates such a thick layer of old paint that it starts to crack and peel. If you have only put a couple of coats of paint on it since the last time you stripped it, it's unlikely that it needs to be stripped again, unless you got a bad batch of paint or didn't apply it properly, according to the manufacturer's instructions..