The report service writes to the database every 1000 samples and retains the information for a defined amount of time.
The following are the default retention periods:
Daily samples (collected every 5 minutes): 5 days (repsvc.daily-samples-retention-days)
1 hour samples (weighted average of daily samples for one hour): 21 days (repsvc.1hour-samples-retention-days)
12 hour samples (weighted average of daily samples for 12 hours): 42 days (repsvc.12hours-samples-retention-days)
24 hour samples (weighted average of daily samples for 24 hours): 180 days (repsvc.24hours-samples-retention-days)
You can tune the report service to write to the database of samples. By default a write is made every 1000 samples. For larger deployments, you might want to increase the number from 1000 samples to a larger sample size.