I've used both Marine Tex & Devcon with good results for several years. But over the past year I noticed the newer Devcon kits from Brownells have a larger container for the hardener, for the same amount of material. The hardener in the 1st one of these kits dried-up & turned to useless crap after only a couple of bedding jobs worth of compound had been used. Brownells replaced it with another kit at no cost, but in that one, the hardener container didn't have the usual foil seal under the lid, and it'd already dried-up before I got around to opening it. Brownells replaced that one too, but weren't too happy about it. Their suggestion - stop buying Devcon & switch to another product.
I called Devcon with the lot no.s of both kits and explained the problem; nope, they won't sell you another container of hardener, and since I'd bought them from Brownells, and they'd sent out new kits, they really weren't very interested in discussing it further with me. My shop's heated during the winter & a/c'd in the summer, and I've never had the hardener lid off for longer than it takes to get the proper amount out of the container. Never had this problem before they started putting the hardener in the larger container, and would really prefer to stick with the Devcon. May try buying a kit from Enco or other industrial supplier. But if it happens again....I've got nothing against Marine Tex, and would be willing to at least try Brownells Steel Bed.