I get asked this question a lot. Is 6 hours enough? Can we get every moment we want captured during 6 hours?
The quick answer is, it depends on your wedding.
Six hour days work well if you have 1 location where all events take place. Most of the weddings that I photograph fall into this category with the popularity of all inclusive venues.
If you are using multiple locations that require more that a few minutes to get from one place to the other, you should consider adding extra time to your day.
Also consider the size of your venue and the places available to take portraits. If you are going to utilize a larger space, a botanical garden for instance, more time to explore during portrait time would be a good investment.
Most wedding receptions I can cover in 90 minutes. We do the introductions, first dance, parent dances, cake cutting, mingle with guests, toss of bouquet and garter, and then the send off. 90 minutes is a perfect amount of time because it ensures that you capture all the important events before everyone is hugging you goodbye.
You might consider extra time if you have a live band, a DJ and younger crowd who will burn up the dance floor, or alcohol. I have found that these type of receptions will cause people to linger at the reception and make for priceless dance photos.
If you are unsure or just want to walk through your day, talk with your photographer about their experiences, tell them about your wedding plans and they will be able to guide you to the best choice for your schedule.