I have yet to come across 60-minute epoxy. Is it chemically impossible to produce such epoxy?

Here is the closest I could find to 1 hour.

Great Planes also makes 45-minute epoxy, but it's not the same as 60-minute: Great Planes 45-Minute Epoxy

The problem that I'm having with 45-minute epoxy is that once the bottles are opened, the unused epoxy and hardener inside the bottles (with caps on) become harden within a couple of weeks.