If you're even slightly intrigued by longevity, you should really watch The Man from Earth.

Takes place entirely on a couch by a fireplace. Thought provoking, suspenseful and emotional.

The film clearly opens up in the end and includes the front porch and the back of a pickup truck.

But yeah it’s a pretty great film and the acting remains solid despite not having a really high end cast.

I think this is one of the few sci-fi works that somewhat got immortality right (and no it’s not really a spoiler).

I tried to find a film that absolutely does not cheat and remains in a single location only. I probably missed some, but they all seem to use secondary places, even for just a minute or two.

But it's not necessarily a bad thing, as this can add breathing room for the audience.

Linklater's Tape (2001) takes place entirely inside a hotel room, no cheating. https://en.wikipedia.org/wiki/Tape_(film)

Ah, excellent, I haven't seen that one, but it's gone up my list now.

Yes, I am actually dissecting it at the moment. It will be the subject of a follow up. See a preview here: https://i.imgur.com/EubgS1f.jpg

Definitely a great film. Poor cinematography can be a turn off for me, but not on this one.