Currently, age is set to four days, as recommended. Once in a while, I want to find something older- say, 900 days, without having to click, delete, change dates, etc., and then reverse changes, as outlined in the original post.
There are 2 ages.
1 - The age the posts are stored on disk (Storage Age).
2 - The age that it displays by default (Display Age).
If you want to be able to examine 900 day old posts, I'd set the storage age to 900, "Post Storage/Use download age" and download 900 days worth of headers. Keep them on disk so, you can load them again later. Then you can load whatever age range you want up to 900 days old. Then set the "Display Age" to 4 so, it only ever loads up 4 days worth when you're examining the groups normally. In that way, you always have the ability to search through old posts while having the quick loading of a short display age.
That's how Newsbin was designed to work. Then you don't have to bother with trying to micromanage the groups.