I also let it rest horizontally on its wheels last winter. It works perfectly fine. But it takes up more floor space than I would prefer. I want to go vertical this winter.
I experimented with many different homespun solutions. Retired guys can afford the time to do that.
Given I'm here in Canada and everything is expensive and/or hard to get, and you cannot put LnGos on this deck, I've learned to improvise cleaning and storage solutions.
I'm going to go with a better version of what I've used most of this summer on an interim basis. I used an old (but strong) folding vertical luggage dolly I had. I broke it but it lasted most of the summer and allowed me to store the deck vertically as if on a homemade Deck Dolly, but with the deck facing the other way on the dolly.
For the winter, I'm going to drop the deck on edge (PTO side down of course) on a full size steel vertical moving dolly with tall handles ($60 CAD for me at Princess Auto). I've dropped the deck using the tractor and straps over my bucket hooks when I wanted to store it after cleaning/sharpening. That worked great. But in experimenting around with what I wanted to do for the winter, I determined I can lift the deck myself manually too. It's heavy but manageable to tilt up.
I put a 2" block of wood on the platform plate to provide stability for the deck when it sits on its bottom edge fins. The wood block lifts the deck off the floor on those fins, so the wheels (and wheel locks) are not resting on the floor. It works really well and sits very stable, leaning against the dolly verticals.
My vent definitely leaks. I'm getting a vent plug for executing this plan. I'll just keep it in a ziploc and loop it over the plug so I don't forget or lose anything.