eh, if it's not broke...
Usually, yeah I would recommend staying up to date.
Up until a couple months ago our hosting servers were sitting behind a pre-1.0 install that had been rock solid for years. But we also understand what was broken in that old of a version and didn't use any of that functionality, most people don't have the luxury of being as familiar with the code base as we are.
I attached one someone sent us nearing 800 days.