If possible, try to record your sessions. This not only provides a back up for students who attend by have technical difficulties, but also provides another access point for students who are unable to attend in real time.
Relevant support guides:
Reminder to Download Blackboard Collaborate Ultra Recordings! Instructors and course staff are encouraged to download all their recordings during and immediately following the last class for their own backup, as indicated on the Course Life Cycle.
Webinar recordings created using Blackboard Collaborate Original are deleted approximately one year after the course end date. End dates are determined according to the standard Arts and Science academic session calendar.