When Peter DuBois was directing Gina Gionfriddo’s play “Rapture, Blister, Burn” off-Broadway last year, a pivotal question arose. Are the characters 40 or 42? Two years might not seem like that big a deal, but in the context of the play, age matters. Two former college roommates meet again after many years: One is a superstar academic who never married or had children, and the other is a stay-at-home mom. They each have a few regrets, and each wants what the other one has.