The Deets: When using the Discourse Gamification plugin, you can create Leaderboards (LBs) for a specific timeframe; however, when you do this the default period does not match this timeframe, and on the Leaderboard, you can still toggle the timeframe and adjust the scoring on the LB itself.
Example:
And on the LB itself, the dropdown still displays and when you choose the different options, it can alter the scoring/ranking.
The Impact
One of our many use cases for Gamification was to simplify and automate our “Member of the Month” (MoM) program. By creating new leaderboards to showcase every month, we want a static view of who our top contributors were throughout the month. Today with the drop down being usable, it can alter the LB based on the date ranges and make it appear that our MoM might be incorrect (especially when an end-user may not understand the effect the dropdown will have on the scoring, which is not something we should expect them to understand). Side note: I know other folks use it for these purposes as well from replies on the plugin topic so the impact here would be greater than one customer 
Proposed Solution:
Ideally, the period drop-down (shown in the second screenshot) would be non-editable and display the from/to date range selected in the settings for the LB.
Alternatively, if we cannot get that, at least locking the period drop-down to “All Time” and not allowing anyone to edit it will show all activity during the date range selected when creating the LB.