I have my USBs stay powered when the PC is shut down, so I can charge various things, but I also run my monitor LED ring through the USB and it serves as a side lamp/background light.
Admitedly this is not fully 24/7, as I do turn stuff off when I leave the room, especially these days as it all costs me twice as much now... but there's no particular harm running them all the time. LEDs have something like 50,000-100,000 hour lifespans, so worst case scenario would be that you burn them out after about six whole years of constant use.....