Pretty sure the tech at my dealership said I should keep my engines (trip 450Rs) trimmed all the way up when not in use. I didn't specifically ask about winter storage and that notwithstanding I don't think my dealer has much experience with 450's.

All that said I would trust you all more than my dealer's opinion.

Up or down for heated winter storage?

False. Should be stored in my garage.

Down. Always down.

I would check the manual / their website.

Which makes me curious? Do ppl boat year round at LOTO?

Not really. Most people are winterized or will soon be winterized.
You will see bass boats out pretty much all year and maybe the occasional OB center console

Page 122.
http://download.brunswick-marine.com.../8m0141652.pdf

This

We run our cruiser almost every weekend, rain, snow or shine all winter. We have a bilge heater that kicks on automatically that I test often. If power goes out we flip the generator on.