You will sit there and hear him talk, listening and paying attention because you love him and choose to honour him, and not because you can’t get up and leave.
And by the way, if I find out that your granddad didn’t have a regular audience when you were home with him, or you leave him alone for long periods just because of Facebook or your computer games, you will hear it. You won’t find it funny at all.
He has many stories to tell and a lot to share. You say that they get boring or that you know ‘the moral of the story’ in them already. I know you know; just learn patience for the ones you claim to love, and for the ones you should love anyway.