Obviously, cold epoxy (below 70 degrees) is next to useless as it is way too thick and pasty to use appropriately, but...
I personally would NOT warm/heat up the epoxy AFTER I mixed it. I would warm it to 85-95 degrees prior to mixing it by putting it in an open heat box, but I personally wouldn't want it to get over 100 degrees even prior to mixing it. Once it is mixed, I certainly don't want to heat it up (nor do I want it cold). Heat makes it cure and begin to set up. The hoter it is, the less working time you have. It states you have a 2 hour working time at room temp (typically around 75-78 degrees) in a shop, but I suspect that at 100 degrees it would probably BEGIN setting up in about an hour to some mild degree. I don't want it to set up at all until AFTER I put pressure on it in the form...as I want a mildly warm (just warm enough to mix and spread easily) epoxy that when I put pressure on it will actually get driven into the tiniest pores and textured surfaces in the riser and limbs. If it begins to set up when you do your first glass layer...by the time your done with the last glass layer (which if your spreading it well can take up to 45 minutes on some multi-lam bows)...I want to know that stuff will still flow and hasn't set up at all...as I have to get the press assembled and pressurized...and by the time I mixed the epoxy to the time I put the pressure on it...close to an hour has passed. This is why I want my epoxy no cooler than 75-80 degrees, but not much warmer than 90 degrees.
To date, I have never had even a cloudy spot in a limb. I probably shouldn't have said that though...because I will end up jinxing myself on the next one. LOL.