Flat-spotting is primarily a thing of the past, from the bias ply tire days. On my C, I had bias plys until this year (they stopped making my size, and the only other comparable size was now radial only and $$$). I changed tires and wheels to a modern LT-Metric LRE. When I drove it to get the tires changed, the tires had obvious flat-spots for a couple miles, but they always became round again after warming up and driving. With the new radial LRE tires, it can sit for weeks to months without flat-spotting (the old ones would have flat spots after a week).