I roll around locally without a spare. I spend enough with Les Schwab on a yearly basis and have good friends working there that I'll just use them to bring me some roadside assistance. I've been pretty fortunate to only need a spare when I've aired down for a long weekend at the dunes. Sand in the bead equals slow leaks. That's for my suburban or Toyota's prior to building the square bodies. My smaller rigs, 33" or smaller tires, I've had numerous flats while cruising the logging roads. I carry plugs to repair the small punctures. When we travel a decent distance with the trailer, I carry two spares in the trailer since Jason, myself and my trailer all take 8 lug. They are matching to the trailer and will get Jason and I to the nearest tire store to repair or replace ours. If I'm out for an extended weekend, say hunting or chasing deep powder white snow, I throw a spare inside the back.
I have a factory mounted spare on my dodge. My experience is that you need to have a spare with you. The plugs work great quite often, but having a spare guarantees the chance at returning to civilization. Sidewall cuts are very difficult to repair and trust when you're doing 70mph down the highway with your family in the rig. I will be mounting a swing out carrier for mine when I build a rear bumper or prior if I can find a body mounted one I like. Suburbans are specifically difficult to do a swing out body mount because of the angle to the rear quarter. The blazer is fairly straight like a pickup bed and the tailgate allows for the mounting better than ours.