In yesterday’s Globe, there was a question about How to cut ties when the old boss won’t let go.
Oh my. If you weren’t sure you’d made a good decision, you know now you have. I actually think there is a better way to leave a job. Assuming you give two weeks notice, here’s what you do:
First week: finish the work you’re supposed to finish. Remind your boss you need to do a brain-dump of all the work you normally do and that your last day is next whenever.
Second week: remind your boss again that your last day is whenever and that you need to do a brain-dump, and that once you are gone, you are gone. (You are under no obligation to provide them with a current cell phone or email, unless they are willing to pay for it.)
If you are in the middle of a hairy project, and you feel strongly about it, you might offer to be available for one or two calls, but I would be wary of this offer. If they accept this offer, you are working for free, when you need to be making your best impression at your new job. If they don’t accept this offer, how will you feel?
So, no, I don’t think you need to answer any questions after you’ve left. If your boss has done what he or she should do when you leave, which is to assign someone to be the recipient of your brain-dump, and if you are not trying to be a jerk about the way you leave your computer files, no one should need to contact you once you leave.
Make your farewell clean. Ask for references before you leave. Ask for LinkedIn contacts before you leave. Be clear that you are leaving. Now you can cut your ties gracefully, and you are done answering questions about your old job. And, if your old boss calls on a Saturday night, who says you have to answer? Maybe spacing the way I do about charging my phone is not such a bad idea 
