I'm not a coatings expert, but I play one on the 'net...I do distribute an industrial epoxy coating, write a spec here and there, do a little training and install a little on the side...
There are a lot of factors which determine product performance. Most of the reputable products on the market do not typically fail and with a legitimate failure, out the retailer, the distributor, mfg'er will try to take care of the client, even when the failure may be to installer error.
With that being said: Upon review of 20 years of case histories, installer error accounted for 80% of product failures.
Starts with determining the proper prduct for your application, i.e where do I boat, environmental concerns - abrasion / chemically / temperature resistant, ease of application, safe to handle, etc.
For recreational boating, the best product and systems are found right here with the cast and crew of BE...Take advantage of the all the bottom paint / painting experiences on this board, can help steer you to the right bottom paint system for your type of boating. There are some who will also provide un-solicited advice as the thread merits.
For the application: Read the Tech Data Sheet - it will give you detailed information on the following points:
Surface prep is key, it the surface properly profiled, free of all bond breakers (dust, grease, oil, wax)
Is the substrate dry / do I have potential hydrostatic pressure issues (not likely on a boat)
Proper mixing of the epoxy / bottom paint coating with the right type of drill, mixing paddle and speed
What are your temperature ranges: ambient air, surface temp and humidty
Produt applied at the proper mil thickness via brush, roller, airless spray?
Application pattern - mfg spec / 2 or more coats applied at 90 degrees to avoid pinholes?
Recoat windows: how long between coats? How is the environment changing cure times?
When is final cure for immersion / non-immersion return-to-service?
Deviation from the application specs can (and do - trust me) affect cure times and inter-coat adhesion failures (top coat does not stick to base coat and flakes, chips, bubbles, etc)
With all that being said, I have never bottom painted a boat, but I am due. I have 3 year old ablative paint and have some chips like Dave is experiencing. I believe most of mine have come from those little hidden submerged suprises I seem to find.
Is Ablative paint referred to as being hard / brittle? Is this the trade-off for a multi-season soap-like wear away surface? I don't know, I haven't done the research on that type of coating.
All I can say when I do re-coat, going with a 100%-solids industrial epoxy barrier coat, haven't decided on the anti-foulant yet.