Good times vs lost memories.
Elite has found the best amount of time for an open bar is about 4-5 Hours. This reason (among many others) is why Elite Private Bartenders offers a base rate for 5 hours. As 5 hours of open bar is exceeded, things begin to get a little "sloppy" and the host liability increases significantly.
Waste is another factor to consider.
As 4 hours is exceed for open bar, guests are much more wasteful with beverages. For example: Guests are more likely to leave their drinks (half full) and forget where they are, over-ordering drinks from the bartender ("I need 10 shots"- 5 left at bar) and simply ordering more than they need. Of course, that's what we are there for; and certainly don't mind. But for the host, this translates to real $ dollars out of your budget. The average waste is about 5-7% for any party or event. Open bars exceeding 4 hours: The fifth, sixth, and seventh hour will skyrocket to 20% wasted (pun intended).
Everything cost more.
All services will cost more as the total time is extended. Planners, DJ's, caterers, bartenders, servers, and event facilities will ALL need to be paid additional for their extra time servicing your guests.
Things you can do.
Especially with weddings, it can be difficult to fit everything in your timeline. Here are some simple tips to avoid extended timelines on your special day.
Tip #1. Don't get married too early.
Typically ceremony time should be between 5pm-8pm, not earlier. As a general guide, you'll want your ceremony to end about 15 mins before sunset.
Tip#2. Note to the bride and groom: You won't have time to party, sorry. :(
This can be a difficult notion to accept. Understandably, because your longtime friends and family have come to see you on your special day. The truth: you are going to be scheduled down to the minute: flower tosses, cake cutting, first dance, speeches, and plenty more. Sometimes couples wish to add extra time so they can hang out and party (I am personally guilty of this at my wedding). Even if you do, it's will not accomplish that goal. So do Mom and Dad a favor, save them some money and stick to the 4-5 hours of open bar. It'll (indirectly and directly) save them thousands overall. - See "everything costs more" above...
Relax and enjoy your ceremony, it might be the only actual time to have to relax. :)