Oops! My water heater...

Well, after over a decade of camping, I did it. I left the power switch on my water heater set to "on" which means as I'm getting it ready for the season I discovered that the water bypass valve was still bypassing and I'm heating up an empty tank of air. I've had the shore power plugged in for several days now, and when I went to check it tonight I noticed a nice warm breeze coming out of the water heater drain, so it appears the element is still working.

So, what have I done? Or perhaps the better question is: Is there something I SHOULD be doing now to avoid more problems down the road?