Vacuum advance pod

I don't see ethanol as the problem. Mine is about 13 or more years old and has always been on an engine that has always run 87E10, and I've always run a manual trans and about 11/1 compression.
Are you running a PCV system?
Why is that important?
IDK, that's just what popped into my head.
I guess the better question is are you having issues with blow-by gasses?
I guess what I'm getting at is; how do you suppose ethanol would get to the diaphragm? Is it not plumbed to the spark-port, which is plumbed to an area in the carb, just above the throttle plate. So for the bulk of the engines run time, the diaphragm would be under dry vacuum.
I guess you could cut it open and inspect it. I do this by grinding off the folded pinch. Then it just falls open. Then you'll be able to tell if it's perforated,ruptured or all soft and wrinkly.