Are you talking about the ring around the lid? I have a Kuhn Rikon that I used for about ten years before I had to replace the old one. I notice that the new one is silicone instead of rubber. Kuhn Rikon gave me this pressure cooker when I was a demonstrator for them in Williams Sonoma. They also gave me a hint to pass on to customers: Every few uses, rub a bit of cooking oil on the ring for a good seal.

Yes that is what I'm talking about. My pressure cooker is Mirro and only about 4 years old. I think its seal is silicon, too. I already tried smoothing some oil on it but that did not help. However, after reviewing an instruction manual online, I tried stretching it and that seems to have done the trick.

I'm still interested in how long the seals generally last---whether in storage or in weekly use.