Between my M Coupe and our old 135i on non RFT's, I've gone over a dozen years on non run flats with one blow out. I've dealt with plenty of slow leaks and carried a plug kit and an air compressor, but I have never wanted, or needed a full sized spare.
Between all the M cars, Corvettes and other cars out there without RFT's and no spare, I think you'd hear more horror stories if there really was a big issue with this.
Learn to use a plug kit and check your tires frequently (TPMS is not very accurate) and you'll seldom have to worry about a thing. Or stick to RFT's, they are much better than the old RE-050's that many of us were tortured with.