A week ago if I brushed my teeth then tried to rinse with cold water it hurt. Also if I drank hot tea/coffee it hurt. So a week ago I bought some new toothpaste,
Colgate Sensitive Pro-Relief (noisy link), and now my teeth don't hurt. As I have already got a (bigger) 2nd tubs it will be a while b4 I know if they are seriously saying "It'll be forever"