Your display cases would be pretty well ventilated though I'd guess - would LEDs in a tighter housing - ie in an action figure or scale vehicle - be ok to have running 24/7 d'ya think?
LED's are pretty efficient, they produce very little heat. I haven't had something on all day before, but I've often had one on most of the day and it was just fine. I guess you could test it out and see how it's doing after a day. The only other thing is that this one isn't just LED's, there's a motor in there for the engines to spin. Motors don't last as long so that would be a risk.