I disregard PvP in WoW. Or, more to the point, I usually don't play PvP when there is some kind of character power progression, and WoW actually managed to make me hate it's PvP. The longest stretch of time I ever played WoW's PvP was getting the School of Hard Knocks achievement on two characters - in the end I just bubbled my way into it (by bubbling any team member who seemed poised to do the task before me) and came out actually hating WoW's PvP with a passion (apart from pesky seasonal achievements - where now, out of spite for WoW's PvP, I won't even attempt to help my team - I never set foot into a BG again).

The MMO where I love playing PvP is DCUO, thanks to the Legend mode (where players use pre-made characters). I'm really looking forward to GW2's PvP, BTW (standard equipment, no gear progression, unlimited number of saved PvP specs that can be switched at will outside combat; there's no way for a character to be simply more powerful than another, or at least no way that the opposing player can't copy in 5 minutes or less).

As for the 30 minutes limit, during week days, it's usually a hard limit. I do my gaming during weekdays on the short breaks I get between work and school. If I'm in the middle of the last boss's fight when the time runs out, I will ditch the fight and log out, no matter what (and, in the process, usually wipe the group, since I most often play as a tank). So, if I'm not absolutely sure I will be finished before my time runs out, I don't even attempt it. Until WoW can provide entertaining content for someone with my gameplay limitations, it's just not the game for me.