I consider myself a fairly long-term, consistent player. I have four level 85 characters, with two more in the mid-70s working up. I plan on raiding at least five days a week, and the days I don't, I still am in-game for an hour out of habit. I read just about every WoW blog, listen to the WoW Insider podcasts, and named my cat Thrall. (If only he were as even-tempered as his namesake.)
Yet I found myself trying to rationalize to my guildmates -- my friends -- why I was going to miss a raid night to watch the NCAA tournament. For me, the opportunity to see my favorite team, the Kansas Jayhawks, possibly make the Final Four was more important than another raid night with my third alt. We lost the game, but experiencing the atmosphere with other fans was well worth it.
Obviously family gatherings (especially if you have kids) can and should take priority over something you have to do in game. However, WoW is far from the most important hobby many players have. What other extracurricular activities force you to change up your WoW schedule?