Today I'm unable to see
Last 30 days options in Achievements dropdown.
This might not be a bug maybe by design. But I would like to know why it is not showing up and in what basis it is shown?
We load the last
n items, for very active users it will go back less time. This is intentional - it's meant to show something for both the very active user as well as the user who only gets reputation a few times per month.
Very active users see their rep very often. Given that the dropdown's purpose is being a summary, we're okay with it not going back that far...that's actually what's intended.