What is my responsibility to my lab after I graduate? I just finished a research-based Masters program, where nearly my entire degree was funded through sponsored research from a particular lab. In the normal schedule of events I should have had time between my final thesis submission and the end of my final's month funding to clean up my files/database work on a shared server. But the week of my thesis being due the criteria for completion was suddenly moved, such that I was no longer able to graduate on time. I ended up having to work unpaid past my graduation in order to complete my thesis. Several months after successfully submitting my thesis I am being nagged to clean up my section on the shared server. I have no intention of attempting a PhD with the lab after. What should I do?

I should add that this has been a recurring problem in our lab, that Masters students are under a lot of pressure to do more in their thesis, but not given time to organize their work so that it can be useful to future students. Once they graduate they get jobs and don't clean up after themselves.
Here's a way of approaching the ethical aspect of this: how important would it be for you, if you were in the middle of your degree, that a recent grad's files were left in a big mess?  Would that affect the finances of the group, because of the files eating up a lot of storage space?  Would your work be more difficult or time consuming, with needed files being hard to find?  Would you have to take some time away from studies and research in order to try to put the recent grad's files in order, for the good of the group?  Would it be difficult for another member of the group to figure out what was what, in the recent grad's absence?

I wonder if you could ask for payment for at least part of the extra time you'd be putting in.