re: How much time has to pass before something is longer at risk for a spoiler?

Depends on the grasp it has on pop culture and how long it's been out.

If I'm going to talk about Star Wars, I'm not going to adjust myself for spoilers. If you haven't seen Star Wars you have a slight problem.

"I don't want to see it because I'm not a nerd, or I'm not interested in that."

See that's where you're problem comes from. You're something worse than a nerd. You're a social outcast. Prep your wrist for the bar code and wear this patch on all your clothes.