I have had a few re-glazed over the years. My sub uses the "Perma-Ceram" system. It is a 2-part epoxy system that he sprays on. Prep work is of course critical, and if there is too much rust around the drain, and it is not removed completely, the rust will migrate to the finish. ("Rust Never Sleeps") I have returned to the jobs off and on and the tubs look fine and have never heard any complaints. However, I don't believe the surface is as durable as a factory finish, just a hunch. Also, Perma-Ceram is pretty specific about what cleaners to use. Anything too abrasive, like "Comet" or any other soap mixed with sanding grit, voids the warranty.