We had a tub and shower surround fit over the traditional tub in June, 2011. It is April, 2012 and Jerry come to replace mildew/mold caulking.
Of course, we too, have the "lifetime" warranty. I was told that Bathfitters would no longer warranty our tub because we weren't using cleaner with bleach in it. We have used the cleaner given to us at the time of the install. We were told that we had to use only that product or it would VOID our warranty.
Jerry said they were telling ALL their customers that when they had to come back. I told him that sounds like a product problem not a customer issue.
He shrugged his shoulders. I strongly recommend you simply replace your bath tub as needed forget about the convenience.