I remember hearing about some city in California, I think it was, that installed LED lights on their Christmas town "Holiday" Tree (which happened to be out-of-doors).
They've had to replace them several times now. Turns out, the squirrels are chewing on them. The old incandescent lights apparently used enough electricity that when the squirrels chewed on the wires they got shocked, at which point they'd stop and amble off, leaving the circuit intact. The new LED's don't use nearly as much electricity, however, so the squirrels don't get zapped, and they continue chewing until the wire either short circuits or is broken. So instead of saving money on electricity, they're spending much more just replacing or repairing the lights.
They probably work very well indoors, however.