How long you stay at a given depth to become saturated depends on what model you are using. If you use only a 5 minute compartment in your model, you'd consider a diver saturated after 30 minutes. If your longest compartment is 60 minutes, you reach saturation after 6 hours, a 120 minute compartment would saturate a diver after 12 hours and using a model with a 480 minute compartment would require 2 days to reach saturation.
Actually, in theory, a diver can not ever become totally saturated without increasing the pressure beyond the point at with you desire saturation. In general use a compartment is considered saturated after 6 times the half time of the compartment. A 5 minute compartment is 50% saturated after 5 minutes, 75% saturated after 10 minutes, 87.5% after 15 minutes, 93.75% after 20 minutes, 96.875% after 25 minutes and 98.4375% after 30 minutes. As long as the diver remains at the same pressure, the compartment continues to approach 100% without ever reaching it. After 6 times the half time, at 98.4375% most models consider it close enough to figure as if it was 100% as little progress toward that unattainable 100% is made after that (of course it also makes it easy to figure saturation points for compartments of 10 minute increments which would <B>not</B> be the case if 7 times the half time or 99.21875% were used).
HTH,
Walter