The Amsoil Signature series 5W30 in my wife's car was changed 12/06/20 @ 93,743 by me. Car now has 99, 463 on it and I'm not worried in the least. Signature series starts out with a TBN of 12.5, it is one of the most robust on the market. I've been using Amsoil SS since about 2011 and UOA since 2012 on Amsoil SS. I've NEVER changed it before 10-12K miles. C'mon man it's the best oil out there, you don't need to change it like Wally world oil.
I have no idea why Amsoil puts that "one year" lifespan on their oil. Probably got something to do with lawyers or new car warranties, neither of which I care about. I have previously run Amsoil over 3 years to get about 10K miles. If you are sincerely concerned, I would suggest doing a UOA, and I know, there's a crowd on this site that would say "oil is cheap, engines are not." But they don't run Amsoil, and I'm not suggesting you do UOA on a regular basis, just to establish precedent and give yourself peace of mind.
What area of the country do you live and how is the car stored at night? Does your garage have freeze/thaw cycles?