This policy was developed because people complained that some people stayed on PCs for long periods of time, even when others were waiting. So we came up with a 2 hour limit when others are waiting. If the lab gets crowded and people are waiting, start a waiting list and check the sign-in sheet to see who has been on for 2 hours. That person is welcome to get on the waiting list 30 minutes after others have been given a chance to use the PCs. These are bad habits around microcomputers, especially keyboards.
Sticky keys are expensive to replace.
Lab assistants working more than 4 hour shifts may have a drink, but please keep it out of sight and away from the equipment. The lab clients are not allowed to have food or drinks of any kind. Yes, some people are into multi-processing. If the lab is not busy you may allow people to use two PCs. Make it clear that they must yield the machine if someone else needs it.