I too have a GENERAC 5500. (2001) It is hard (time-wise) to start up even in warm weather. Do NOT have it crank longer than 15 seconds (says the owners' manual) or one might overheat the starter. They say it...I do it. It takes a good 3-4 tries until it starts. And I notice the starting RPM increase the closer it gets to starting. The it fires up...and I wait about 20 seconds before putting any kind of load on it. My unit, however, when the temp gets below 30 degrees will not start no matter what. Crank and crank forever...no start. So I just leave it alone until the next, say, 40 degree day.
I start the genny and the motorhome engine every two weeks during winter storage. Run both for about 1/2 hour, Some here on the forum say "don't bother", but I feel better...at least keep the oil flowing and the batteries charged. Then, if no snow (or chemicals) on the ground I take it out for a short run maybe once every month and a half .