I had a 22 R1T for three years and used auto ride height the entire time. My 21-inch road wheels lasted for 41,000 miles. I think using conserve mode is harder on the tires than auto ride height. I was very careful to only use conserve after I was up to speed on a highway or interstate. Starting out in conserve mode from a stop is hard on the tires. I currently have AT tires on my 25 R1T and once they wear out, I agree with Golfer04 and will get some all-season tires for better range.Assuming the truck checks out, if you are concerned about range don't stick with the AT tires. Trade them in for a 20in all weather tire (I've owned 2 Ts with AT tires and they stink). They suck in cold weather too. Might be good if you rock crawl, but daily driving they are noisy, don't last and in cold weather easily lose their grip (I'm in central Illinois).
Also, if you are a new Rivian owner & care about your tire longevity don't use "auto" on the suspension height. Select standard and turn auto off. You lose .01 percent in efficiency on the highway, but your tires last. Dropping suspension down shifts the vehicle weight to the inner half of the tire which tears them up.
That doesn't match any numbers Rivian has ever published for a gen 1 quad. I would ask them for a report on battery health.Rivian sales just texted me and said “The 280 miles is in Conserve or 2 wheel drive”, suggesting it is normal. I guess I will check if someone w/22” wheels want to trade or maybe I’ll buy a second set of wheels.