I don't think there is a set time for an orbit. You've got to consider the actual situation and the reason for the orbit. If it's to provide spacing for a departure of an aircraft, or to slot you in behind GA traffic, ATC may only need you to orbit for a minute or so. So something faster than a rate-one turn would be appropriate (say 30 degrees AoB at 100 knots). But if you need to orbit because there's an A380 landing, ATC may need to hold you for three minutes or even more. In that case a rate one (17 degrees AoB at 100 knots) would be more appropriate.