According to the blog:
[I]f you've contributed something worthwhile to the site, you should keep the reputation for that even if it eventually gets deleted. "Worthwhile" here is defined as,
- A score of 3 or greater
- Visible on the site for at least 60 days
"Visible" seems a little loose, and I'm wondering if that's what was meant. I could ask a "great" off-topic question that gets closed the same day, and if it's not deleted within two months then I get to keep all the rep from it.
In contrast, the posts that (I believe) we're targeting with this are questions that were formerly accepted, and through a lot of participation got some content considered valuable. Most would have been open for at least 60 days, I would guess.
I wouldn't want to mess up rep from any of those classic posts, but it seems that the "visible" criterion would allow rep gain from off-topic/bad questions to continue indefinitely, so I think it should be tightened up a bit. There must be some way to distinguish between rep-worthy deleted questions and questions that simply weren't deleted fast enough, right?