It depends on who is eating them. I'd have no problem boiling week out of date eggs and keeping them an extra couple of weeks. Having said that, I have a stomach made of titanium and can pretty much eat anything. If you are going to be feeding them to young children or old people, I wouldn't keep them much longer than a week beyond the sell by date.
I absolve myself from any responsibilty for any illness caused by my advise so use at your own risk!