The rate of the chemical reaction that occurs in two-part epoxy when it is curing is highly dependent on temperature. For those that care, chemical reactions in general are characterized by the Arrhenius equation, which, simplistically says the rate of chemical reaction doubles for each 10C rise in the process temperature.
Preheating your 30-minute epoxy to reasonable temps, say 120F instead of room temp can be useful. By the same token, leaving your epoxy job in the unheated garage overnight not only will slow the cure, it also means that the epoxy will never come to a "full" cure. That is a whole discussion by itself, but for model airplanes using wood construction, it is mostly irrelevant. I would make an exception here for actual composite structures or epoxy composite jobs that depend on monocoque strength.
I think people may be getting confused between two things going on at the same time. When you hit the components, or the uncured mixed epoxy with heat, you are reducing the viscosity, even while you are accelerating the cross-linking. Grossly overheating the partially cured material--such as really getting on it with a heat gun--will reduce the viscosity but I would bet that you are also permanently damaging the material strength, notionally breaking chemical links that have already been made, and won't get remade as it cools. So as one person said "who would do that?"
And then there is the extrapolation of a rule that's not a rule: if you heat a completed assembly that is put together with epoxy it comes apart.... That's just an observation that has nothing to do with the original question of curing rates of epoxy. What may be helpful to understand is that epoxy is a thermoset resin. Cheap epoxies do not have very good hot strength. And epoxies that have been chemically altered with "stuff added" can only get worse. So you hit them with a heat gun that can put out air at least 450F (model usage; home or industrial guns put out at least twice that) and you're above the temp where hobby epoxies are going to have much (any?) strength. So the parts separate easily. And since it is not a thermoplastic, smooshing the parts together and hitting them with the heat gun does not "glue them back together."
Modelers are pretty creative and often insistent, so we do what we think is good enough for our needs. Here are examples I have seen promoted, many of which I have tried, along with some of my comments:
1. Thinning epoxy that already has a lot of filler in it (any 1:1 mix epoxy product has filler) is a make-do solution. There are epoxies available that are very low viscosity. You will hear guys tout their favorites, and the two that I have used both worked fine.
2. Thinning epoxy with a solvent means that the solvent has to evaporate too, and must migrate out of the unsolidified material or be trapped inside. Anything trapped inside is just weakening the epoxy. A really poor choice, which people will advocate simply because they have some on hand, is isopropyl alcohol. By definition, it has water in it. Water that will get trapped. That will alter the cure. Combine it with cold temps and you have a good chance of making a weak, rubbery, partially cured mess. Acetone is probably a good deal better since it should evaporate out of the mixed uncured epoxy more completely, but it is still a "make do with what you have" solution.
3. Continuous heating of the material still to be used so that you can "save it" and finish the job just makes everything harder to do right. It won't be as strong and it poses handling issues as both ends of the spectrum: enough heat to get it to flow without running away everywhere, or; not quite enough heat so that you are trying to spread a stringy glob.
4. Epoxy paint is not epoxy glue or resin. Paint may also be two-part and it may say "Epoxy" on the can, but if you try to hold something together with it, let me know before you fly so I can stand way back from the circle. Waaaay back.....