That's my experience. I PIF every month, keep my utilization in the single digits, and I'm struggling to get my nose over 700. The only baddies I have are some delinquencies circa 2007-08 and a collection or two from the same period that's since been paid off.
Nothing more I can do; at some point time will age these delinqy-dinks and my score will rise
Starting Score: 653 (11/1/2011 TransUnion)