I read somewhere that if your drysuit at the end of its life gives you 1 dive for every pound that you have spent on it then it is doing quite well. I am not sure how good that is, but I have just spent 59 pounds plus 12 pounds postage to get new seals on my suit, and I've got 90 dives over just under two years on the suit (ignoring its original cost, thats 90 dives/71 pounds), so its just beginning to get its money back, but it will be a very slow process.
Diving = money pit. But we all know that anyway
