I usually will change out a head for flavor or output before then, and I'm spreading the load between several tanks at the very least. I actually wondered if the question was sarcasm.
That it goes open is more interesting. I've seen them suddenly go to one coil wrap only, very hot, which then pops. I can only guess the coil lead comes loose.
Currently I'm replacing coils by rebuilding the heads using Fasttech's NR-R-NR pre-welded coil assemblies, 7 cents each + effort (getting faster). Rewicked with cotton. The new Kanger organic cotton SOCCs aren't done right.