Its not an exact science bakkies. You kind of get a feel for it. I have different time periods for different dams, and also if i know my bait is in a good spot i dont want to take it out until it really has to. About 6 hours later for me. But if it gets a couple tugs ill leave it for 10 hours. But a dam like shongweni ill leave it for no longer than 4 hours. But ahni know the dam and the bite patterns