Everybody I know is jumping up and down ready for spring, and threatening to take out a contract on Old Man Winter. (It is worth noting that ONLY in northeast North America has this winter been colder than normal, everyplace else in the Northern Hemisphere, this winter has been particularly mild.)
The reason you winterize, of course, is to prevent damage from freezing temperatures. This only happens if the temperature drops below freezing for enough hours that the pipes freeze. Frost overnight doesn't usually cause a problem, but like Reader1 said, if you dewinterize during the iffy season, you have to be vigilant and ready to re-winterize or do the furnace bit.
We're just ahead of you on the warming trend here in Virginia, and I've been threatening the DW with a weekend camping trip for a couple weeks. I've returned the water heater bypass to normal, but have not put any water in the TT. But this weekend looks to me like a prime opportunity. I'm READY to go CAMPING!!!