I can't or won't necessarily stay late or show up early to accommodate your schedule. If you don't get the experiment done by the due date because you did not spend all the time in lab you could for it, then that's your problem. Occasionally you may have to wait for a particular reaction to finish, or you may complete a procedure early. This is a good time to work on your notebook, reports, or other experiments. It is not necessary but may be helpful to write an outline of the experiment before you do it.
People often find that it takes less time to do the experiment and fewer mistakes are made.
I often do this myself. Useful References 1. R. C. Weast, ed. S. Budavari, ed. Aldrich Chemical Co. Milwaukee, 1998.