I'd been waiting for the plastic to start fatiguing on my Rossignol Course E boots which I bought in fall 1996, and it happened, but in one of the heel pads, which crumbled at the back edge. Looked around online and I found one source for replacement pads that only shows applications back to 2005.
While doing this search, I learned what a score I had with these boots, and why they've been so outstanding for the last 18 years.
While I agree that I've gotten my money's worth out of them, I also don't see a reason to stop using them, since the heel pad is replaceable, and they're still fantastic.
If you have an explanation based on chemistry why the heel pad crumbling at the back edge where the boot first contacts the ground in a step, is a sign that the (different ?) plastics in the shell may also be degrading, please share it.
If you can suggest a source for a replacement heel pad, that would be fantastic.
Last, a bit of boot mechanics. My lay knowledge tells me that the heel pad can't be involved in the friction interaction with the rear binding (Look P10) since that releases up. Moreover, if a part of the heel pad is missing, it by definition can't be involved in the friction interaction since it isn't there. If you have a physics explanation for why this line of reasoning is wrong and I should absolutely not wear the boot with the heel pad damaged, because it could prevent safe binding release, please share it. The top of the heel block where it mates with the rear binding is not compromised.
Thanks all !