There are several ways to know if people are using TeamMood on a regular basis.
Usage overview over the past 30 days
From your Analytics view, take a look at the Usage Chart to check if people are using TeamMood in a regular basis:
It shows the number of users who used TeamMood in the past 7 days, the ones who used it in the past month, and the ones who never used it yet.
It's cumulative, eg, on the graph below, it shows that 75% on users used TeamMood in the past month (the ones in the past 7 days + the ones between 7 and 31 days).
This information is also shown in the Reporting view thanks to the Distribution pie chart in the Participation section:
Weekly participation rate
You can get an export of the weekly participation rate for a team from your Export Center.
Each line is the participation rate for a week, from the beginning of TeamMood usage:
You'll get an overview of the usage trends from your Periodic Digests that you get by email or Slack etc.
Also find these trends in the Reporting indicators.