All that the estates do is try to prolong the life of the original artist, but they do it bureaucratically and dogmatically and frequently stupidly. They have no flexibility because they're not artists.
Therefore I don't take them too seriously. In the end they fall away. Then metaphorically speaking, you can paint moustaches on the Mona Lisa, but the Mona Lisa is still smiling underneath. You don't actually deface the painting.
But the best way of working as far as I'm concerned is with a living author, because you can have a true collaboration and find out what the play means. I'm currently rehearsing a revival of Amadeus with David Suchet and I have Peter Shaffer (the playwright) with me.
I'd rather have estates than not. I think there should be a transition period between the death of an author and a free-for-all.
I wish in some ways that Shakespeare had some trustees to stop directors cutting him up and mangling him. They cut Shakespeare with a reckless disregard and the critics all nod approvingly.
If it was done with Mozart or Wagner there would be rioting in the streets. It should be cut if it is absolutely incomprehensible to us, otherwise we have no right.
I worked with Beckett and he was absolutely wonderful, flexible, very human. He wasn't dogmatic or at all restrictive. On Waiting for Godot, I side with Sam. If he had wanted to write a play about two women he would have.