After completing a meal a person has 72 minutes (according to some opinions) to bentch. Once this time has passed he lost his opportunity.
Say that during a meal the rav gives a shiur or you're in the middle of listening to an mp3 shiur or a video shiur, does that prolong the 72 minutes?
This shailah comes up when the rav gives a shiur in shul during seduah shelishit on Shabbat.