Installation requires reboot -- immediately?

Hi, I'm doing my first project involving Terminal Servers. The client
has Win2003 TermServs and we're working with NSL 3.51.3.

After installing NSL on the TermServs, I expect that it will say they
need to be rebooted. Does that need to be done immediately, or can it be
delayed without any side-effects for users who log in between the install
and the reboot? The requirement that the first login be an
administrator -- is that the first login after the install or the first
login after the reboot?

These TermServs are used for a LOB app, so they can only be rebooted
during the middle of the night. I'm wondering if I could do the install
during the day and let their admin reboot the servers remotely at night.

Thanks

-Mitch Terlisner