Hmmm, I drove mine in St. Louis. It was there for at least a decade. I never had any major rust issues with that particular truck, but I was better to my vehicles at the time. There was some bubbling around the quarter panels, but nothing major. It was an 1987, and was pretty beat up, so I wasn't worried about it being perfect.

The thing with the toyota truck I noticed mostly, is that despite cosmetic flaws, it still ran great and was pretty sound functionally at 230k. I had a dodge dakota that fell apart around me and spun a bearing at 160k. The drivers side door hinges actually rusted completely out.

I had a 1987 MR2 in St. Louis for four or five years as well, and my friend had it for three or four before that. It had issues with the rear quarter panel as well, but otherwise was good.

All anecdotal, and the St. Louis winter isn't a Michigan winter or anything like that, but there's my experience fwiw