Looking at our proxy console we see the cache is only holding files for about 30-60 minutes, 30% hits. This figure is the same for two different caching configurations:

proxyserver1:Aging=default, Control HashT=1024, HotNodes=66000, Location=3 12GB Trad.volumes, 512 dirs.
proxyserver2:Aging=7d,6h,20m,7d,7d,0m,30m, Control http=450MB, HashT=256, HotNodes=50000, Location=3 12GB Trad.volumes, 384 dirs.

Any suggestions for better caching on these two very busy servers with 2000-6000 connections, ~500 fills in progress?