E3D left on all night!! Whoops!

My understanding of it is that any time you leave an extruder heater on, you run the risk of scorching the material inside it, which may not clog immediately, but can build up and make it more likely to clog later, especially if this happens repeatedly.  But the E3D is also much less subject to that problem because of having an all-metal one-piece interior which provides fewer places for scorched material to stick to.  So you may have no problems, but you may have just made it more likely that some future time you slip and leave the extruder on too long, or even just in normal use, there'll be a clog.  It's more of a death by a thousand cuts thing than an explosion.

Now, time for me to be corrected.