In most other cases, I would recommend that you investigate bathtub refinishing. But since you have already done that, the surface of your tub is compromised for further coats of refinishing paint. After all, that's all it is: painting. Mind you, it's painting done by trained and experienced professionals (except in the case of the guy who did your tub, apparently), so it does have its merits. But coat upon coat of paint really won't work very well.
Here are three options...
Suggestions for How to Fix Your Bathtub
- Continue to Fix Your Bathtub. Based on what you say, you've been doing this for 16 years and are pretty well sick of it. So, I doubt this is an option.
- Refinish Bathtub Again. Even though you don't have a great surface for a second coat of finish, I think that a good refinisher could help you eke out a couple more years from the bathtub.
- Install a Bathtub Liner. A bathtub liner slips right into your tub, covering up all of that bad paint and other ick. This is more expensive than refinishing, yet cheaper than a completely new bathtub.