Why can I lose communication with a Windows 2008 R2 network connected printer?

Question

Printers

The situation is the following. There is a machine with Windows 2008 R2 x64 installed on it, acting as a terminal server. Each user has several network printers connected (different machines act as print servers, both with XP and with Windows 2000). Periodically, namely 2-4 times a day, communication with printers disappears (in the devices and printers tab, they are displayed as connected, or not displayed at all. Printing is unavailable in both cases). When you try to reconnect to one of these printers, the system reports "unable to connect to the specified printer."
The problem is easily solved by restarting the spooler service, but after a while it reappears, which is extremely unpleasant. I, as a person far from system administration and setting up various peripherals, cannot understand in which direction to dig in order to find the root of this problem.
Please throw in some ideas.
At the moment, I just set the spooler to restart automatically (every 10 minutes), but this is a crutch, and users can press "print" just in the interval between stop and start =)