Tire life?

I have 15,000 lbs. on my triple axles, and run the Sailun S637 at around 95 psi. Any more than that translates to a very rough ride in the trailer and things really get thrown around.

I tried running 110 psi at first, but the trailer rode horribly. I've lowered the pressure 5 psi at a time until I've reached the best compromise between carrying capacity and smooth ride. So far so good after 5 years and 20,000+ miles. The tires look great with no excess wear or odd wear patterns.

I vote for a chance complete change at four years. “Tread” isn’t usually an issue on TT tires. Regarding pressure, if you are a tire expert run them at whatever you want but the manufacturer says use the pressure stamped on the tire. Not being an expert I follow manufacturer recommendations but the I was in the Army! lol

See https://www.sailuntire.ca/plt/S637st.html 110 pounds

She’s close to 16k loaded and I’m thinking 8k axles. I’ll air them up to 110psi. I feel like coming up on 3 yrs sounds like they are good on age. They look good.
I’ll be selling the coach once I get there and buying a house. Just want to make sire the next owner is set as well. I’m dropping it for a few small repairs before I sell.

80 psi in a 110 psi rated tire isn't the best idea nor is psi recommendations from a minimum pressure chart the best idea either. Were talking tires on a trailer tech...not tire on a tow vehicle tech.

For 7k-8k axles I would use max sidewall pressures for best long term service.

If you have 5.2k-6k axles then I like what these folks have to say on the subject;

rvsafety.com

Tire Load and Inflation Ratings

Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure.

ST tires I would change out at 4-5 years regardless of milage.
LT tires which is my preference I would change out at 7 years regardless of miles.

The Sailun tires are pretty descent. I would expect 5-7 years.
As for the air pressure, I would weigh the rig. My first thought is you should air them up.