How should I phase questions to discover if a job has a stay late culture
Tactfully. You want to avoid giving the interviewer the impression that you're against all forms of overtime, as occasional overtime ("crunch time") is typical in IT. Because of that, Alison Green recommends not bringing this up until the offer stage:
I would wait until you’re offered the job before you ask about this
Yes, ideally you could talk about this as part of a discussion of
workplace culture in the interview itself, but I would really rather
you not give them any reason to misinterpret that question that stage.
(The risk is that they’ll think you’re asking because you’re going to
be a pain in the ass about working anything over 40 hours, ever.) So
it’s safer to wait until they’ve already decided that they want you.
Once you get an offer, when you’re asking whatever other questions you
need answered, ask about typical hours too. Say something like this:
“What are typical hours in your culture? I.T. needs can pop up around
the clock, of course, but I’ve worked places where 70-hour weeks were
standard and places that were much closer to 40. Where did the person
previously in this job tend to land on that scale?”
You could also come out and be really straightforward about it, if you
wanted to: “I’ve worked plenty of 70-hour weeks in the past, but now
I’m at a stage in my career where I’m seeking more balance in my life.
The nature of I.T. work is that there will always be some after-hours
and weekend work, sometimes with no notice, and I’m fine with that —
but I’m looking for something where that’s more of the exception than
the rule. Is that something that sounds like a fit with your culture
or would I be setting us both up for problems by having that mindset?
Source: how can I avoid jobs that expect 70-hour work weeks?, Alison Green, Ask a Manager, 2011-02-02