Today, something mysterious happened in my current game. I came back to my Aether portal after quite a long abscence (must've been weeks in MC time) to find it extinguished! It was no big deal to activate it anew, 'cause I always carry a water bucket with me. But since then, I'm wondering what could've caused it to deactivate. I can't think of any overworld mobs that could extinguish it - never heard about Endermen carrying off water blocks or the like... :-D
On the other hand - I was really far away from the portal most of the time, so that it's chunk wasn't even loaded most of the time. Do the portals just stop working after a certain time of inactivity? Did something like this happen to any of you? Curious to hear your weird portal stories... :-)