Let's talk about how long your wedding photographer really needs to be at your wedding reception. Knowing how long your wedding photographer could be at the reception could save you money in the long run.
You'd be surprised how many brides come to me wanting me to be there from the moment they wake up to the moment they plan to leave for the reception. While being there for the departure of the bride and groom is always lovely it normally means 2-3 hours and hundreds of photos you really never wanted, mostly because everyone is drunk and looks terrible. Keep in mind that most DJs can have all the “important” events done within and hour or hour and half after dinner is served. If you really want a "leaving" picture possibly think about something leaving your ceremony. This way you get those photos without chancing most of your guests leaving or everyone looking horrible because they are on their 4+ drink. ;)
Of course, talk with your wedding photographer about what photos you want captured and if they can make it happen in less amount of time. :) As with all things not every shoe will fit everybody, so in the end do what you need to do, just a little suggestion. ;)