Two things: are you running low tyre pressures? I had a Bridgestone BT 19 (front tyre) that wore like that because I ran it with lower than recommended pressures.
I like the Avon's too (Storm 3D X-M), currently at 12,000 miles...
If you're having trouble sleeping here's everything you wanted to know about tyres and tyre wear (it's a US site so some references have to be reversed since we ride on the other side):
http://www.rattlebars.com/tirewear/index.html