how would you feel about a new SM on the gig calling you a few years down the road for pointers? Would you be willing to talk about it? Would you expect to be paid for the consultation? How about if you left the show under less-than-favorable circumstances, would you feel the same way?
It would not surprise me to learn that this sort of discussion (if uncompensated) would constitute an Equity violation. It
may also violate a contract you have with another company. (At the very least, while the clauses aren't common, I've definitely seen contracts which expressly forbade certain employees from working/consulting on/assisting with other shows for the duration of the contract.)
In terms of non-Equity shows, this has happened to me 2-3 times so far. (Once with a show I'd left, twice with shows which were being revived without my involvement.) The method I've worked out:
1) You're going to comp me a ticket or let me attend a run-through rehearsal, depending on which stage you're in. I will be taking notes.
2) We will then have a working meal, ideally take-out at someone's place. (So we can get out the books and go over notes and really get into the meat of it.)
3) I will claim the whole exercise as a tax deduction. (Maintaining good contacts and excellent interpersonal relationships, especially with companies for whom I have previously worked, is absolutely essential to my future employability. This dinner-and-a-show [but we won't call it that, now will we!] is a networking opportunity, will keep me in good standing with a previous employer, and might also include mentorship or industry-service opportunities. In short, it counts as work.)
As to whether you
should do it, yes: you should. I'm not being entirely dishonest about everything I've said above: this is an opportunity to make some contacts, see how a piece you've worked on has developed and grown, do a little mentorship and industry service, and it will also make you look good to a previous employer. (Who is, of course, the likeliest person to employ you in future.)
As to whether you
must do it, no: you don't
have to. If you're morally opposed (working for
free?! NEVAR!!!!!1!) or genuinely too busy or you left for damn good reasons, you're certainly under no obligation.