I know, I said that there aren't any rules about when you have to finish up your spring cleaning and that it doesn't even have to be done by spring. However, actually getting everything finished, period, will become more difficult as time goes by. When the warmth and beauty of the new season is beckoning to you from outside your window, do you really want to be knee-deep in a closet reorganization? Before you know it, you'll be in the dog days of summer, trying to find beach toys in the garage and realizing that once again, you weren't able to get to that room in the spring.
So here's my crazy advice: start early. Those doldrums of winter, when it's too cold and dreary and blah to go outside, are actually the perfect time to spring clean. If you have a yard, you don't have any of that work to do. If you live in a place that gets lots of snow in the winter, you can keep yourself busy (and warm) inside with your cleaning tasks. Then you can get outside guilt-free in the spring.