I’ve worn one 6 times now on flights sat in economy. Not a pleasant experience. Part of the problem is the airline in question (Iberia) doesn’t turn on the APU until around 5 mins before departure. It means the cabin is extremely stuffy and warm. Things improve slightly once you get going, but it is still uncomfortable wearing a mask for such a long time. Perhaps a more expensive mask would be more comfortable? Many of the other pax didn’t seem to be fiddling with their masks as much as I was.