Skills - Reoccurring vs. Time Limited (days)

Summary

What is the difference between Reoccurring and Time Limiting a Skill

Content

Hello,

We are using Skills mapped to Assignments and Certification Tracks for our safety compliance training (which is mostly offsite).  And we've been using the "Time Limiting a Skill" to show that the expiration of the Skill when achieved.

But what does "Reoccurring" a skill do?  Are there other benefits? Since I can't seem to make it work in our system I wanted to check with others before I put in a service request.

Thanks,

Rachael