Need Advice

Looking for comments on two tyre, but linked, questions?

I’m currently waiting for delivery of my third Yeti.  The previous two I had for a combined 6 years and about 36K miles per year.  For about 5 years I’ve used a set of winter tyres, on 16” rims, and changed then with the supplied summer tyres.  They still look to be in good condition and have plenty of tread, certainly enough for another season with a good margin.  I’m concerned about the age of the tyres and overall safety.  I’ve read various recommendations that typically range from 5 to 10 years and then change them?

With the new car scheduled for July I’ve been thinking of moving away from the summer/winter tyre combination and moving to the CrossClimate tyre.  So when the new car arrives I could do a few miles on the supplied tyre till the autumn then buy a set of CrossClimate tyres, storing the OEM fit tyres.  As I change the car typically every 3 years I’d probably need to refit the OEM tyres prior to the MOT or selling.  This would make financial sense if the answer to the first part of the post were ‘buy new’ winter tyres as the cost would be almost neutral.

Any thoughts or advice appreciated.