Hey, glad to see this thread has life still - 42 posts.
Well, I have plodded 10 mile training runs three times now, and 12 miles once. On the 12 mile run I did 5 minutes run/ 1 minute walk. On the first ten miler, I plodded continuously with no walk breaks. On the other two, I experimented with 0.7 miles run / walk one minute and run one mile / walk the first minute of the next mile.
And my fastest average pace? The 5/1 12 mile run! Maybe I'll stop experiementing now and go with this (I'm training for my first half marathon on May 22nd). It just seems so counter-intuitive!