HI
Usually the resin working temperature is specified and between 15 to 20C for epoxy and other ester based resins
The problem with heating resin to lower viscosity is the pot life triggering the exothermic gelation before you want it,while you use it.
I usually go for about 25C on epoxies with slow hardeners but just above 15C temp on esters enabling me sufficient working time.
Once I'm finish laminating or infusion I raise the temp of the part in the mold to 30C with a heating fan to circulate warm air for 3 hours to help faster curing followed by post cure.