I don't know if you have already done anything with your tub, but I am a comercial installer for a company called Am-Bath, I install bath tub liners and shower surrounds in hotels accross the country, I have done thousands of them. I also occasionally replace ones that we have put in previous and now is time for them to be replaced. Most of the ones that I replace have been in place for 15+ years. First of all the liners are made out of an acryllic not vinyl. They are very resistant to chips and the like, They do scratch if not cared for properly but so does the fiberglass that they put in new homes now days. However major scratches can be repaired rather painlessly, unlike fiberglass which is very expensive to repair.
Our company has franchises that go under the name of ReBath. Our liners are warrantied for 5 years and they give you a list of approved cleaners.
Another advatage is cost, you can have one of these done 3 or 4 times before you approach the cost of a new tub, or shower surround, that gives you about 30+ years of use out of one tub. Second they don't require a plumber, and the whole replacement can be done in about an hour, (20 minutes if I do it he he he). So there you go. Hope every thing works out for you if you have any questions feel free to ask.