How different might this UOA have been if the time frame had been, say, two years instead of around six months?
Hmm. I've considered Amsoil but I doubt I'd ever run Signature Series near long enough. It would take me two years (or more!) to rack up 25,000 miles. For peace of mind, I'd have to do a UOA every time I reset the OLM, which would quickly eat up any savings I'd get from doing a 2yr, 25,000 mile interval.
If I drove as much as the guy in the OP, then we might be talking.