In fairness,

I play EVE Online, after 3 months or so I get sick of it. (took 8 years to get this way though)
I play Lord of the Rings Online, after 3 months I get sick of it.
I've been playing ARR for around 3 months.

Tera lasted about 3 months,
DAoC lasted about 3 months,
FF14 1.00 was 3 months stints. Any of the other 50+ MMO's I played most had a 3 month shelf life.

FF14 is one of a list of 5 that I actually come back to though. It's still one of the prettiest MMO's I have ever played. It's just kind of shallow.