The Activity Log records account-level actions by team member: role changes, settings edits, document deletions. It is the first place to look when a number changed and nobody remembers changing it.
Data Retention sets how long records are kept after they close. Regulatory minimums (DVIRs, HOS, driver qualification files) are enforced as floors; you can keep records longer, not shorter.
Terminated accounts are purged 30 days after termination. Export first if you are leaving.