Wow how many times can one thread be brought back from the dead!?
My take on extended drain AMSOil is this: you pay double for the oil and leave it in twice as long. 25000 miles is their rating for cars on a light service schedule, 15000 is what average drivers should use (and is closer to the other new extended service oils claims) AND they say it is limited to a ONE YEAR oil change interval. So if you drive 15k miles or fewer, it's still a 1 year OCI oil. Yes it is an astonishingly good oil. No I don't think I could stand to go 25k miles unless someone else with this engine did it first and showed their UOA results.
That said . . . this is the wrong website for starting a thread like this anyway
The alternative is to pay half price for high quality synthetic oils and good filters, and change it twice a year. Six of one, half a dozen of the other, no net gain . . . unless you see a fuel economy rise with the AMSOil, which some people do report.