Although it is not possible to pause the lab, you are allowed eight one-hour extensions for a total lab time of 9.5 hours including the initial 90 minutes. You can click away and then come back and resume your lab where you left off.
We don't have the capacity to leave labs running for a long time, however, you can start the lab at the beginning of any module. Use the table of contents in the lab manual to jump ahead to the module you wish to take. Ideally, you should take a lab when you have time to complete one module in the maximum 9.5 hours. And you may take any lab as many times as you like.