Should I grant an extension on an extension? A student asked for a homework extension due to unforeseen circumstances in their personal life. I am generally accommodating about this type of thing if they come to me in a timely manner, but this student did not follow up until a week after the homework was originally due. (It is online homework, so I have to re-open the homework in order for them to work on it again.) I asked him to email me which sections he missed and he did not.

He spoke with me in person again two weeks later and again I told him that it was fine, but that he needed to email me right away and come to me in a timely manner about these types of things in the future, or else I would not be so accommodating. This was the end of the class week, so I was planning on giving him the weekend to work on these assignments and have him turn them in at the beginning of the next week.

However, he did not email me until the night before our class, so I would have to give him time this week to complete the assignments instead. At this point, the assignments were due over a month ago, so I am wondering if it is reasonable for me to tell him that he is no longer able to complete the assignment since he waited 4 more days to email me.
This would, to me, seem to depend not on dates and length of delay, but on the reasons behind them. I can easily see deciding in either direction, based on what the student gives for an explanation. 

Everything may be perfectly explainable, including not sending emails. Or you could decide that the student was just slacking. But base your decision on the reasons, as best you can determine them, not just the time factor.