I've been running 4T for over a year now. My engines look as good at rebuild time as they did when I put them together. I run it in my flatheads, animals and modified animals without any issues.
As a humorous aside, I've found a use for some of this used oil we change out every race night - I store it in a gallon jug and use it for chain bar oil in my chainsaws. They seem to thrive on it.
