I have been through 2 sets of stones, and one set of E4s, working on the 2nd set.
Currently at 83k on the clock.
I'm an air pressure fanatic.
41 in the rear.
Was 40, but now 38 in front since the Traxxion upgrade.
Before every ride, if it is not that according to my FOBO, I fire up the air compressor and make it so.

I too am wearing out the middles before the edges, but many trips to Dallas from NW FL to visit parents will do that.
I'm actually finding that I like the E4 in the rear for the treadwear and tar snake management, and the Bridgestone up front for rain traction.
I know most people will not mix brands, but that E4 in the rear does a GREAT job and there is nothing better than the Bridgestone for rain traction.
My $0.02.
Your Mileage Shall Vary
Cheers,
Steve