This year has been film photography, drone piloting, 3d printing, vector graphics, javascript, speaker building and learning arduino.
As soon as I get hooked I go overboard. Like with film photography I have gone to the extent of buying like 3 different types of cameras,experimenting with as many film types as I can and looking at learning to develop the photos my self in the coming weeks.
From a psychology perspective (of which I don't know more than psych 101), it also could be about an "alpha-geek" hierarchy. This probably comes from a desire to be the smartest in the room on <<topic>> which often happens in geek circles, right? Don't we often get into the "I started coding at 6", "I used a mainframe", etc. one-upping. Also known as establishing dominance.
I have a (bad?) habit of spending all my energy learning as much as I can about a new topic until I get either bored or distracted, and move on to the next thing. Never fully learning one thing (jack of all trades, master of none).
Some examples in the last year: Etching circuit boards, woodworking, ZBrush, speaker design, reading Cyrillic, photography, Erlang.