I buy tires on the rim at Northern when they go on sale for $89 or $99. Its a little more than I was paying for tire + mounting, but I can do it myself - rather than sitting and wasting time at a tire shop.
I find that the front axle tires wear faster than the rears, so I also rotate front to back. With rotation, I get about 1 year out of set of 4. I also carry a repair kit, tire sealant and a 12v air compressor/battery jumper/12v plug/inverter combo.
I rotate them Also, i do the same with dually's