I don't have a hitch, but I do have a FSS and a FSS is vacation insurance to me. If I'm on vacation or going on vacation, I don't want to be limited to having a donut and finding a replacement soon. Couple that with a hitch, and you don't want to be pulling with a donut.
What are the downsides of carrying a full-size spare? It cost me $50 to buy a cosmetically so-so used MDX wheel (even included the TPMS sensor). The tire didn't cost anything because I am using a tire that was worn and ready for replacement; putting enough miles on it to get me home would be no big deal (although I'd make sure to use it on the rear). And while any increase in weight is going to affect gas mileage, we're talking about a difference of maybe 10 pounds on a 4000-pound vehicle, so any effect on mileage is going to be negligible.
Knock on wood, to this day with about 400K total vehicle miles, I have not needed a spare change during vacation. I've had to change a few times, but local driving.
Within the past five or so years, I have had...
- One tire on the MDX that developed a leak, enough to set off the TPMS but still had enough air for me to get the 15 miles home (where I could swap on a winter tire, then take the regular tire to get fixed)
- One tire on the Integra that was pretty worn, almost ready for replacement, that went dead flat about half a mile from home, so I just drove home on it
- One tire on the Integra that blew out when I drove over rode debris on the highway 40 miles from home, so I swapped the spare on and continued to my destination, then returned home
- One street tire on the NSX that blew out 100 miles from home (I was having problems with that valve stem, so the pressure probably got low) so I swapped on one of the track tires I had with me
- One street tire on the NSX that developed a leak after an off-track excursion on grass, so I swapped the spare on and drove it 130 miles home
Those are only the incapacitating tire experiences, and I'm not mentioning several times when I've picked up nails and screws that I then had repaired.
I've probably had worse experience than average over that time. But OTOH I have enough experience with tires that changing them is no big deal for me.