We have an "ocean sounds" CD that E. made for Loo when Loo was little, to fall asleep to. We played it for him every night and at some point, we got tired of turning it on and off, so we just left it on. It's been going non-stop (and I mean, round the clock) upstairs in our bedroom for, I dunno, four months now? (Volume is low. It's background noise; we don't even notice it anymore.)
The other day Loo and I were up there and I had a hankering to put on some tunes. I thought about it, but I'dve had to turn off the ocean sounds. And all I could think was, "I can't!! That'd kill four months of uptime!!"
UNIX Admin in former life, obviously.