Also, rotating ACCELERATES wear! When a tire is worn-in on a position on the car, it's ~already~ in it's lowest wear mode. (wear/mile) Change the position and it must re-bed to it's optimal "pattern" and wear is accelerated during that process. Here is the best overall plan- Buy new tires in Fall, drive them all the way to next Fall then rotate the good ones up front for the 2nd winter. Next year buy new tires. If you drive a lot more, get 2 new tires every Fall for the front and rotate them to the rear asap in spring to "preserve" them for the next year. Variations in this scheme are necessary, but this is the basic plan. Personally, I use 2-3 sets of all-seasons. (I drive 30k a year) Fresh for winter, intermediates for spring and fall and summer "smokers". Sets are rotated down the line as needed, but usually I get 2 good winters out of a set if I take them off asap in spring. I always have just the right tread for the season. My woman has a CRV, she has a winter set (fresh all-seasons) and a summer set that are the worn a/s tires. Same thing, 2 good winters out of a set is the target.