Yes, it's possible to do several training sessions with Vector during the same day.
However, the program has a barrier that will not allow you to log in again until two hours after the latest completed training session.
In general, we recommend to let the children train once a day until all 40 training sessions are completed, as this is the way it was tested. Training too frequently may also result in the children getting too tired and losing motivation. But training two sessions a day every now and then, for example, to catch up after absence is okay. See what works best for each individual and for your organization!