I purchased one of these cushions almost three years ago before going on a trip because I know those airplane seats can be a beast after a few hours.  It did take up some space in my carry on even in it's deflated/folded state, but totally worth bringing.  This made sitting on the airplane a lot more comfortable.  That said, I have been using it every single day since then and have had no issues with it.  I deflate it a bit if it feels too high on a chair and inflate when I use it sitting on the floor.

This has been a great investment for me.