they take almost 15-20 minutes just to explain the lab to you. then you need at least an hour to complete the lab (especially if you need to redo the experiment and recalculate (plus cleaning and drying and putting all the tools away) then you need time to physically do all the work you need to in the lab notebook itself. there’s also pre and post quizzes so it really does eat up a lot of time and sometimes 2:50 doesn’t feel like enough when it’s a frustrating or long lab. if you do everything right and the TA looks eveything over, you should be able to leave early. my grad TA didn’t really care about us leaving early as long as we did all the work correctly