The Pitmen Painters is currently playing in NYC at the Manhattan Theater Club.  This review, written when the play was in London, may interest you.

… a rich tapestry of art, drama and recent history … with personal recollections of Richard Lyon …

What makes a particular play run and run?  No single property surely, but some of them are well illustrated by The Pitmen Painters now back at London’s National Theatre for the third time, and for a 4-month season.  I would hazard that two such properties are interrelated:  breadth of appeal and the efficient weaving of an optimum, slight, degree of ambiguity (ie several messages, none too heavily stated), achieved by having several strands in the dramatic development interwoven with enough coherence to not fall apart.  Rank ambiguity is tolerable in the visual arts because we can choose to walk to the next picture, but not in a play;  we can’t reasonably disrupt the performance by leaving before the end of the first act.  Waiting for Godot was a success but a rare one, in what is historically a very minority taste.