When I used the foam I didn't warm the components above ambient temperature (it was in the nineties at the time), but I did take the step to warm the compartment I was filling with a space heater. A gallon of component has a weight of whatever, and will weigh close to the same after expanding. If a given amount fills four cubic feet when warm but only three if used when a bit cooler (don't ask where I got those figures), it's a little extra weight per cubic foot, but the biggest difference is the stuff is kind of expensive and you want your money's worth! If you have to buy more to fill all the compartments you plan to fill, it's costing more and adding some weight to your build.
If you warm the components it will react more quickly, I'd think about that if your weather is cool and the components are cool, but if it's already warm I'd let it be. I've seen photos of instances where mid-mix the stuff started reacting like crazy, practically exploding out of the mixing cup, so don't stand across the shed from where you want to pour, and don't disturb the stuff once it's out of the container.