At the moment you can't do either of these. The IP assignment is only done via a local pool of addresses on the PIX, anbd there's no way to tell it to assign a particular address toa particular user . Similarly with login times, there's no way to define specific idle times for specific users, it's a global parameter that gets assigned to all VPN connections.
You would get this functionality if you connected into a VPN3000 concentrator, but unfortunately the PIX doesn't (and never will) have all the features that the VPN3000 has.
