Not sure what you mean. Most days there is no need to warm packs up. When there is I just keep them in the cab or if it really is that cold out, on the floor under the heater. Good to go as soon as I drop them in.

But I think this is a silly point. I never thought about the time to fuel/start, etc. Now one thing that is a little different is once you have the pack in the plane, you are ready to fly instantly. No worries about starting, warming the engine up, low idle killing the engine, etc. I especially like never having to think about the engine dying while flying. The end of the dead stick as we know it!!