Do you mean how long it takes for a game that's only available in Japanese to be translated into English and be sold in the US?
It can vary, but I think it depends a lot on how well they think the game in question would sell in the US, how well it does in Japan, how quickly it can be localized/translated, that sort of thing. I'd give it a little less than a year on average, although that may be just for more popular/hyped games. Diamond and Pearl were released in September in Japan, and then were in the US in April of the following year. Just as an example. Other games I looked up were about the same amount of time.
If you mean the other thing, I ordered something that was shipped from Japan once and it took two or three weeks to get over here.