[skyking1]

Internal deterioration is not visible, and that is what the X number of years recommendations are based on. Don't dwell on how it looks. It is literally only skin deep and not the critical structures. They look at those after a tire blows and causes an accident, or not.
All that said here is my recommendation, as a former tire tech, commercial driver and mechanic.
If you have snow in winter or heavy rains, I would run those tires all the way to next fall.
There is nothing as nice as having fresh skins when the weather turns sour, and you are likely past the worst of it. The 5/32 is kinda my bare minimum these days for weather driving. I would not worry about rot or internal condition at all. The extra tread is priceless when it gets snotty.

 

[skyking1]

I have dedicated snows that did not get put on this year, but I would be wearing them now if I lived in your area
I have some slightly smaller studded tire for my 3500 SRW 4X4, on steel rims.
stock sized studded snows on alloys for my diesel Beetle.
Some 18" 3 peaks for my wife's tiguan on some stock alloys. These are all Craigslist sets I get cheap.
I like lots of good tires. Since my wife works from home and I have a company truck, and all my family moved to this side of the Cascades I did not need to put any on.