There is a surprising amount of variance in when turkeys fly up. Depending on gender, location, weather, and pressure turkeys may fly up 20-30 minutes before sunset up to completely dark. On rainy, dark days they may even fly up in the afternoon.
I figure I kill 30-40% of my toms in the afternoon or evening. Generally you have to be much more conservative with your calling and decoys. Toms will come in quietly and alone much more often than they do in the morning. Soft purrs and clucks and scratching is about all I do in the evening.
To me the real value of afternoon hunting is that I know where they turkeys will be in the morning. It's scouting with a gun, and that information is invaluable. I'd rather kill them in the morning, the show is almost always better, and some times I let them walk in the evening depending on whether I'm guiding in the morning or closing in on a season limit...
Think ahead of time about how you're going to make your escape without bumping stuff off the roost. If you don't know where they will roost, be very conservative in your location.