Mine has been outside since I bought it 2 1/2 yrs. ago. It's a tin job. I don't 'formally winterize' it, but do perform some off season checks, etc. I have a custom cover from Tracker that I keep on the boat all the time.
During the winter months, I use it, but not as much as the balance of the year. If I get to a time where I've not run it in 3-4 weeks, I'll put the hose/flusher attachment on it and run the engine for a short period.
Spring, I do the lower unit thing, bearings, batteries, etc. to make sure they are all ready. Since the boat is nearing 3 years old, I'll probably do a more formal job this winter, specially since I will have used the boat this year considerably more than before. Last year - maybe 8-10 trips to the lake at most (family health problems). This year, probably at least 30 days on the lake at a minimum. Next year, I expect that my number of trip days will be in the 40-50 range. For me, that's quite a bit.