If you will also use the RV during the summer, it will likely be a good idea. Like others have said, the size can be a major issue, but only you can decide if the RV has enough space for long periods of living. And I agree that being north of Florida is too cold for too long. Heck, even the northern half of Florida is too cold for me and I am from Montana. Go South, Young Man.
If your only intent is to go south for the winter and not RV in a traditional sense, buy a condo, buy a park model or buy a second home. Better investment, easier and more space. An RV isn't going to save you any significant amounts of money over one of those more traditional options. It will just shift the costs around.