What storage space is reasonable to offer your kids when they leave home?

My two young adult children are leaving home this weekend. They have boomeranged back and forth for the last couple of years, but this time I think (...hope...and pray....) the moves will be more permanent.

But we're going through a lengthy negotiation over how much of their stuff they can leave at home. They want to leave all the rubbish they have accumulated over the last 20 odd years. My response to that they can go and hire a lock-up!

I think I'm down to agreeing they can leave one chest of drawers each! And then, when they're gone, I can have my own office cum study!

What do you think? Am I being mean or too generous by half?!