One would assume you could return close to the same focus as before but for taking flats what is it you'd be focusing on? For your lights you focus on a star. If you remove the camera and/or change the focus you have to wait for another star to focus again - then it's too dark to take flats. My thoughts are if the focus has changed then the diameter of the dust motes have also changed as well and any other optical defect so your flats will not work as good as they could or should. What I've done in the past is on my portable system - I pick the whole thing p and carry it in the house or garage for the night. Then the next day I drag it back out a take my flats. On my pier mounted system I just shut down and cover it up for the night. If you have a small enough OTA you could use the white screen of a laptop in a pinch or make a lightbox from the many plans online and then take your flats right before to break down for the night.

Thanks Russ, I figured with my luck I could waste the whole rainy afternoon and maybe I did but at least I had something to do. I saved 20 shots at 70°F and a similar number with everything the same at 55°. I was reading in Michael Covington's book on DSLR Astro that there is about a 8°F span but I will try to stick with the 5° range you suggested. I just found his quote,"Theoretically,the dark current of a silicon sensor doubles for every 8°C (15°F) rise in temperature." Therefore I think your 5°F range is a good one.
I may have lucked out on the focus because I haven't taken any other pictures since the last time so my camera focus should have still been decent unless there was a temperature adjustment.

I am looking at a Sony @550, this camera has a CMOS sensor as opposed to CCD, any comments please Thanks Al