With 90% to 95% of weddings out there, it's not feasible that a DJ spend more than 20 hours on said event.
Let's look at a high demand client, and the wedding is 7 hours of performance time, and let's just say you have to set up 4 sound systems (un realistic), AND you have to set up a large light display, and Up Lighting. Let's say you have no help, and have to do all of this yourself (fault of the DJ's). Let's also say it's a far, far drive at 100 miles (not probable, but totally possible) Also, let's say you need to meet with client 50 miles away TWICE before the wedding, AND do a site visit. ...Let's take it to the max
All the the time invested: (Keep in mind I am taking these time examples to the max, and certainly should not be typical for any of us)
Client contact: 10 emails back and fourth (Time spent emailing - 90 minutes) Two Phone Calls: 1 hour
1st Meeting: Total Time: 3 hours
Contract: 5 minutes
Venue Visit: 5 Hours (Total time traveling in traffic plus 1 hour venue meeting)
Second Client Meeting: Total Time 2.5 hours
Wedding Prep: Songs downloaded, Up Lights Dialed in, charged up etc. : 2 hours (Can you seriously say you spend more than 1 hour downloading music these days for a single wedding, maybe another hour for lights?)
Trip to get Tux Dry cleaned (As if this is added into each wedding) - 15 minutes total
Loading Vehicle, and Double checking you have everything you need: 1 hour
Time
Travel to venue: 2 hours
Load in and Set up: 3 hours (Seriously, can you really say you ever spend more than 3 hours for load in and set up?)
Wedding Ceremony/Cocktails/Reception: 7 hours
Tear down and Load Out: 1 hour 45 minutes (It was a tough load out facility, and those 4 sound systems and all those lights took a lot of trips with the 2 carts you brought)
Drive Back home: 1 hour 45 minutes (Late at night it shouldn't take as long going home as it did getting there)
Next Day:
Load Out of vehicle back into your storage area (garage, house for many, storage unit or office for others): 1 hour (This is pushing it, shouldn't take more than 40 minutes
I come to a maximum time spent on a single wedding to 32 hours and 15 minutes. And this is certainly a very big stretch.
My typical 6 - 7 hour wedding booking takes up 16 to 17 hours of my time...Sometimes 15 hours depending on location. A 4 hour wedding reception only will take up 13 hours...Sometimes less if it's a close location.