Hello folks, this is my first vehicle with these size/type tires. All other vehicles I own are cars with low profile fun flat tires that hold their air pressures much longer than these TRX tires. I inflate to 38 cold as per factory (for street). All 4 tires must be serviced it seems once every 3 weeks or so. The car tires last longer. Is this normal for big truck off road tires like these? Thanks!