Do padded seat cushions help when you are traveling on a plane for long periods? The type you'd buy for a car seat or something is what I'm talking about, or do plane seats have enough cushioning for that long of a duration?
All plane seats I've sat on were soft enough not to cause any discomfort.
A seat cushion may however be useful for very tall persons by allowing them to sit more naturally despite the limited leg space.
I find they help on all flights. Typically on short flights (up to 3 hours) our corporate policy only lets me have economy tickets - and even an hour in a normal aeroplane seat causes me intense pain as they appear to be designed for people with very short torsos, so a lumbar support cushion helps minimise this pain.
On longer flights I expect a bed or at least a good seat, so they are not a problem without a cushion, but having a cushion does let me relax better.