I've never been able to figure out how you get "extra mileage" out of the tires by rotating them. Yes, I understand that some of the tires will wear out quicker than the other tires. But, it seems that you should be losing material from the same tire at the same rate, i.e. the left front is going to lose 1cm of rubber thickness over 50,000 miles regardless of how the tires are rotated.
The only "benefit" that I can see is that you spread the wear among the 4 tires more evenly, so that when you need new tires, you need to replace all 4. I prefer to run them until the front tires need to be replaced. Then, I rotate the back tires to the front & put the new tires on the rear.