Starting from 7.0.1 (not released yet), the queryAnalysisSamplerConfigurationRefreshSecs and queryAnalysisWriterIntervalSecs server parameters are configurable at runtime (i.e. not just on startup). 

Description of Linked Ticket

Currently, the server parameters for the periods of the periodic jobs for refreshing query sampling configurations and writing sampled queries to disk are configurable on startup only. Although users are unlikely to need to configure these periods, we should still make them configurable in runtime.

Here is an example of how to subscribe to changes to a server parameter, and here is an example of how the period of a PeriodicRunner::Job can be updated.