I realised this ...

If you stack wheels on top of each other the one on the bottom has the weight of the other three (75kg ish) resting on it with the tyre taking the strain. Using a tyre tree eliminates this and each tyre is 'unstressed'.

I have though heard that tyres are best stored on a rack in a vertical/upright position. Not sure it matters too much.

Aiming to switch mine over at the weekend.

My tyres take the strain of about 1,800kg between them every day

Only kidding I know what you mean

Snehvide had her snowshoes removed today and the summer sneakers put on.

Wear left on the winters are: 7 mm on the fronts and 8 mm on the rears. Total mileage on the winter tyres is 25,000 km. When they were put on in the fall, there were about 8 mm left on both front and rear, so most of the wear was on the front and less than 1mm worn on the rears over the 9000 km driven this winter.

Switching front to back at each change still seems to work well. On average all 4 wheels have equal wear when in use. It looks like there is at least two more winters left in these tyres, or about a 50,000 km (32,000 miles)life.