Mine has split once in the two years I've had it. I had no indication, however, we left the lights out for three days while out of town, came back and had two BTAs.
Mine has had that sortof cleft down the side for months, but has not divided yet. I got excited when I noticed it, thinking it would divide again, but so far nothing.
I would pay close attention to its mouth, like the previous reply said.
Jenn