How long do pictures take?

Our ceremony is at 5:30. The photo location is only about a half hour (at most) from our ceremony site). Our photographer has us down for 2:30 as the start time for the photos.

We're not seeing each other beforehand and we're not doing any preparation photos or anything like that, it would just be the bridal party and immediate families so we can get them out of the way and do our couple photos and all families together photos during the cocktail hour.

Is 3 hours (or really 2 I guess when you take out travel time and all that) enough time to get all the photos done or should I make the time longer?

I was running late the day of my wedding, we were supposed to go take pictures at 4:00, and I think we wound up getting there at about 4:30 , we left at about 5:45 so I think 2 hours is plenty of time.
(I also had 14 people in my BP and it still didn't take that long.)