A PhD Chemical Engineer who makes and sells high quality epoxy told me that it does indeed have a shelf life, and that old degraded epoxy is not as strong as fresh product. Since then, I either toss my old degraded epoxy, or use it for non-critical filler purposes.
Somebody else here said that a Customer Service Rep at Brownell's told him/her that he/she could salvage the old degraded Accraglas in a similar manner to this microwave heating. I still feel that is just poor judgement. Many chemical compounds simply don't stay fresh forever. Epoxy is not bourbon or fine wine. Exposure to air, heat, light, etc. all can have a negative effect. And negative consequences too.
I think I'd rather take advice about old degraded epoxy from someone who has a Doctorate degree in Chemical Engineering, and who actually makes the stuff. Of course, 39% of the public also believes that Biden is doing a great job too, so that proves there's no accounting for tastes... right Billy?