I'm sorry, I can't go with that.
Again, you're asking someone to present in front of the committee. They need to know how much time they're going to have, and 10 minutes is a consistent time frame. If you say that it's at the call of the chair, then it puts the chair in a really bad position in trying to balance the needs of her party—and she is not really neutral—and what is right, and she will always be under the accusation that she's stacking the committee or that she is doing things to benefit the Liberal Party instead of being the chair. I think that's why it's important that you have it nailed down at 10 minutes.
As I said, if there is a unique scenario, then the chair and the vice-chairs should talk about it and proceed as they see best, but you have to have the vice-chairs involved in that conversation.