I never want to see my baby with a spare on it. ever. If you start getting low then pull into a gas station and inflate the flat and limp to a tire store. I've got warranties on all my tires so I don't care if it destroys the tire. If you get a blow-out then that's what road side service is for.
On long trips there is nothing preventing you from putting the spare in the trunk area. 99.9% of my driving is city/suburb. Always a tire place within 5miles.
Of course everyone's situation is different. We can sit around and talk about the "what ifs" all day. I had a flat one day in a Toyota Avalon only to find out that my full size spare was also flat. $h*^ happens, deal with it
