Why do remote users find that all printers have disappeared from their sessions?

The only way to clear this is for a domain admin to connect and restart the spooler service. I feel that this is fine temporarily, but there seems to be a bigger problem. This isn't a constant problem, but a few times a week is enough. There are no specific errors in the event log. Any thoughts on what we should do?

It sounds as though the spooler service may be crashing, possibly due to a poorly behaved printer driver. If you've recently added a new one, try removing it to see if the problem goes away. Barring that, make sure that all of your installed printer drivers are compatible with Terminal Services. There is no definitive list of Terminal Services compatible printers (however, you can call the printer vendor to get this information. Make sure that you are not using any kernel mode printer drivers. Also, try uninstalling all printer drivers and slowly add them back, one at a time, until you find the one that is not reacting well.