One of the questions a reader sent to me recently was, "What if clear stamps won't hold up over the years?" I don't know if anyone knows the answer to this for sure. I know that some of the early clear stamp company's stamps, like CTMH, did not last. The first set I bought from them turned to gel. They did replace them but only after I posted about them refusing to replace them on a public board. The consultants got upset and mass e-mailed the company and before you knew it, I had a replacement set.
But, I do think the newer ones are made of something different. They surely do stamp much better.
If I ask myself how many of my 10 year old sets I still use, the answer is 2 or 3 and then only very rarely. So, if my stamps don't last for decade after decade, I am not going to be that upset at all.