No They are not indestructible They are little chunks of glass that can easily shatter or chip with just the right bump. What makes them tougher is that they are Solid chunks of glass around the diode instead of a hollow bulb. Stocking a few extra LED bulbs for certain flashlights would be an expensive task and most LED lights are near impossible to replace the bulbs in. LED Maglites are the best bet to stock up on Spare bulbs in either LED or incandescent styles. If I recall the spare bulb in LED Sold Maglites are still Incandescent ones.

EDIT: I Also forgot to mention Trying to find the proper LED bulb for most basic LED based inexpensive flashlights would be a difficult task.