My rifles have seen a lot of temp swings over the years, particularly heat. I'm sure the humidity was high enough when mixed, temperatures were for sure out of range (it's Texas, 65-85 is a 15 minute swing range here) so both factors probably contributed to the degradation of the epoxy over time. I've installed a couple of barrel liners using AcraGlas and chilled it per Brownell's instructions for longer pot life, so far so good, so I'm not sure the lower temperature limit for bedding cures is entirely accurate, or may be only a recommendation for bedding actions due to tolerances and not necessarily a lower limit for the chemicals to work properly. Nothing cures correctly in high heat, not paint, not urethane, not even cyanoacrylates.
The stuff is ok and I've used a lot of it for little jobs, but lean toward the others I mentioned for everything now except for skimming in scope bases, which is a job for red Loctite.