1.A year or two. Give the film time to have been seen on dvd/blu but in forums, it is always safe to have a spoiler warning just to be safe.
1a. From what I can gather, I haven't seen This Is 40, the 'spoiler' they give is wrong anyway. *whistles*  I agree with Doc about TV spoilers, it is a lot harder to tell when it is ok to give them. I hear on other podcasts people giving spoiler warnings to, say The Wire, which has ended but not many people have seen it and  can still find it on repeats or on dvd.

2. Yup but I think it's safe to say we've all done it even if by accident.

3. If I know the person and what they like, I'll drop hints as to

4. Don't think so.....

5. Yup. Nothing major and my shitty memory is refusing to help me remember exactly what but I'm sure I have.

6. I read the end of The Sixth Sense by reading the back of the soundtrack a mere hour before going to see it at the cinema.

I like the poll format. Imma follow it.

1. That would depend on the spoiler itself. If it's about a major character dying in a TV show, it's awful - but it won't ruin the whole show for you, as the show probably isn't about that character only. Now, it still is a spoiler and it should avoid being told for a certain amount of time, but if the whole movie is based on it, I'd say this amount of time has to be far greater.

To be honest, I hate spoilers so much I don't even consider such a thing as public domain for them. A warning is fair when talking about a movie, and I don't see any reason why anyone would go like "Oh what the hell, it's an extraordinary movie but it's twenty years old, you can't possibly care, can you?".

2. Most definitely. When people tell me "There's a huge twist at the end but hey, I'm not telling you anything", it feels like a spoiler to me. As Doc Submarine said, if you're expecting it, it won't work as well as it should.

3. Not further than the official pitch would. Setting up what the movie talks about is enough, and if the person wants to know more, hell, let them watch it.

4. I never would. If anything, it would cause the opposite effect to me.

5. I think it happened once, but it was so long ago I can't quite remember it. Hating getting spoiled makes you wary about it.

6. Back when I still watched Dexter, someone spoiled the season 4 ending for me right after I started it. I was NOT happy, especially since it was, and still is its most thrilling season to me.

But I have a weapon now. Tons of people around me watch Game of Thrones. But I'm probably the only one who has read all the books. They'd better be careful.

Talking about The Sixth Sense. I still haven't seen it, but I already know what its great Shyamalanian twist is. It's old stuff now, it's become a joke - even Cox says it in Scrubs. But the fact that I already know it is probably a good reason why I still havent watched it. It certainly does lower the excitement.

...I'm quite the spoiler freak, ain't it.

EDIT : Dave, you bloody aussie bastard.

As I recall, the soundtrack to Episode One was released slightly ahead of the actual movie - or there were announcements about the soundtrack beforehand, something like that - in which it was revealed that one of the tracks was titled "Qui-Gon's Funeral" or something similar.    So, oops.

1. As a rule of thumb, I generally don't spoil. Whatever it is. When people haven't watched Fight Club, I don't instantly go "Well, then it's ok, because it's an old film now", instead, I think they might not even have heard of it. So, I just encourage them to go see it. Trying to explain Cabin in the Woods is hard, so I just tell them it's the best scary movie ever, because it isn't a traditional one. And they should just trust my judgement and go see it.
1A. Same rule applies. Although Norwegian TV stations spoil them all the time. Guessing that you've already seen last week's episode, and then do flashbacks from it while previewing this week's episode. I hate it. Instead, just watch it. If the spoiler is actually a spoiler, I won't spoil.

2. Yes. They'll be expecting a twist. But also no; because if you don't inform what the twist concerns, it could be irrelevant whether or not it's a spoiler.

3. I tell them the general plot/story without giving away too much details, leaving them wanting to see the film. I did that recently with Looper. "It's a film about time travel. There are these assassins called Loopers, whose victims come from the future. The twist there, is that their final contract is themselves, 30 years from then." That actually worked well enough.

4. Depends. I had to explain how Time Lords can regenerate. It's a spoiler because if you didn't know, you'd think Tennant's Doctor dies in the season 4 finale, and the show would end there. But if you know how it works, it's not a spoiler per se, so it's ok.

5. "what? Rose is okay, what are you talking about? She got her Doct- Oh, snap, you're only at series 3. NEVERMINDMOVEALONGNOTHINGTOSEEHERE!"

6. Never, as far as I know. I stay away from info about something I haven't watched. Like the plague. And if I don't, I just don't care. Example: I knew how TDKR ended before watching it, but I wasn't that interested in watching it to begin with, so I didn't care.