There is already a "screen on" option in the 'now playing' tab. It's very handy whilst driving for example.
Unfortunately, this has to be enabled every time you want to leave the screen on.
Would you mind considering adding this to the settings?
I suppose it depends on a few variables whether users would want that.
Like when connected to power, wifi and/or bluetooth.
Many persistent apps (like syncing apps) use this kind of "power-saving" schemes.
thanks for your time