I’ve never had an issue with rotors permanently warping, despite being a heavy rider who does some reasonable descents (for the UK). I feel like overall the basic steel rotors Ive had on cheaper bikes have been less problematic than higher end Shimano ones.
A much bigger problem that affects cautious riders dragging the brakes on long descents is boiling the brake fluid - I’ve felt that start to happen to me while stuck on a long winding downhill in traffic, and I know people who’ve lost braking while descending on hilly cycling holidays.
See also Richard Branson.