PageFunction.KeepAlive property

Hi,
I have a class that extends a PageFunction:
public class MyPageFunction : PageFunction<object>
{
public MyPageFunction()
{
this.KeepAlive = true;
}
}
Think of this PageFunction as a central Navigation Hub when launching a
Wizard. So, depending on user input in the Wizard, MyPageFunction controls
where to go next. I need to set KeepAlive=true, because there are many state
I need to keep track of during the navigation.

Everytime I launch the Wizard, I will create a new instance of MyPageFunction.
My question is, at what point does each of this instance get destroyed, if
ever? If not, I'm looking at a huge memory leak issue!

thanks,
Setiono