It's sensible to build some slack capacity into your scheduling because it increases your ability to take advantage of unexpected opportunities. If you (or you

It's sensible to build some slack capacity into your scheduling because it increases your ability to take advantage of unexpected opportunities. If you (or your staff) are all 100% committed to one project (and the schedule is based around this estimate) then you have few choices if another low-effort but high-payoff project comes along. On the other hand, if you (or your staff) tend not to be fully utilised at all times then you will have reserve capacity to pursue these bonus opportunities as and when they arise.