Old questions are great if you are looking for questions to answer.
I have received a lot of upvotes from the older questions. The questions are still live as such after 7 days as this is separate from the Steemit platform.
You have raised a good point regards the curation of an older question and I will do an experiment and check. I randomly selected a question that was 12 days old and placed a small vote of 10% on it and it shows up in Steemworld.org as a big fat 0. So that says no curation after the 7 day window exactly the same as Steemit.
There are some great questions that are older than 7 days but your answer is live and current so it counts.
Well It doesn't make sense to upvote it but you can just drop a comment to show your appreciation if you would like. As the window of rewards is set on 7 days, so does the curation rewards as well and you will be likely to waste your Voting Power/Mana on upvoting post that are older than 7 days.
I generally endeavor to answer questions, regardless of whether they are old. Possibly the OP still needs his inquiry replied. I probably won't get any upvotes, however that is not too imperative; the appropriate response will at present be there and somebody will think that its helpful in the long run.
I've watched out for a lot of old demand. It tells the essential advertisement spot, who will all over cast a ticket it up. A number have changed their picked answer to my new answer.
In perhaps 90% of cases regardless, it does nothing. No one else appreciates it. The OP doesn't see it, there are no votes up, it doesn't get picked, and whatnot.
Specifically I answer them inside and out increasingly now and then