At the end of the day our goal is to have filled spots all of the time. So, if you will have spots free at the point these clients need you and there is no $$ loss then I wouldn't charge them. However, if you are leaving a spot unfilled for them they need to understand that it's lost income.

They can either pay for the spot now and it's there when they're ready, or they wait and take their chances that you may not be available.

Personally I don't even interview until i'm in the 3 month zone before the spot is needed. The only time I charge holding fees is for current clients that go on mat leave and want to hold the spot until they get back. And they're basically paying for the space.