monitoring participants time on the session

Yes, paid accounts have access attendance reporting, which includes when each participant joined, left, and overall duration in the meeting. Keep in mind, only meetings you've hosted after the upgrade will have reporting available.  A meeting could have been scheduled before the upgrade, but any sessions that took place before the upgrade will not have reporting. This article has more info: https://support.zoom.us/hc/en-us/articles/201363213-Getting-started-with-Zoom-reporting