Remote Desktop Idle behaviour

A little bit of background:-
Terminal Server (now called remote desktop) running on a Windows 2003 server.

Group policy specifies:-
The session will diconnect if idle for 3hours.
A disconnected session will be logged out after 3 hours.

The unwanted effects:-

1.
When an active session is idle for about 10-15 minutes it goes to sleep, bringing the session back into focus and waiting a few moments (20-30 seconds) seems to let the user carry on as usual. This is not wanted, ideally I would like 'keep alive packets' to keep the desktop open, even if that requires extra bandwidth and cpu to maintain.

2.
Some users say that after this time idle sometimes instead of 'hanging' (going to sleep as above) their connection drops. The leased line is up for the duration of this time.

Bandwidth is not an issue, neither is latency. I'm guessing that both of these issues can be resolved at the client side... but I might be wrong. The servers are in a datacenter on a 10mb line, the clients I have tried from a 100mb leased line in another datacenter, from a 512kb leased line at the office and from 2 adsl lines from different exchanges.

Anyone got any extra info or ideas?