How can it "not last"? Epoxy's pretty hard stuff. Mine has been around for well over a year and other than just starting to yellow (or I like to think, age!) it's doing fine.
Sure it won't be as good as a Watchmaterial one, but it's a whole lot cheaper.
BTW, if you want the best non yellowing buy "clear casting resin". It's used to make nick knacks and furniture. Resin table or bar tops, etc. Problem is finding small enough packages. Maybe a craft store?