When changing resolution it shouldn't take 30 seconds to revert. If the screen blanks out because of an invalid resolution 30 seconds is too long to wait. 10 - 15 seconds is more than enough time for someone to cancel, but 30 seconds can be tedious when you don't know what resolution your device supports. Using neon on my HTPC, I had to use trail and error multiple times as I didn't know the resolution of my TV. I figured out that I could use 'Esc' to revert and skip the countdown but most newbies would not try this. Maybe also add that using 'Esc' would cancel the resolution setting to the dialog? Thanks.
It has been reduced to 15 seconds for Plasma 5.24.