Jacko_G
Blackballed
My putter grip has worn more due to bag rub than anything else. It also gets a fairly regular clean. It's 3 years old, and will probably be changed at next grip change more due to asthetics than effect.
It's not like it's subject to the same abuse as an iron or woods grip.
I'd suggest its used at least 10 times more than any grip, even just an hour putting practice gripping in the same place for an hour will wear it out with the repetitive hand placement.