There is no broadcast time limit set by the Live:Air Action app. Note that the original Live:Air app from 2015 had a 30 minute limit which could be unlocked through an in-app purchase, but this 30 minute limit does not apply to the newer Live:Air Action app.
However, individual streaming platforms may enforce a time limit for your stream.
For example, Facebook allows a maximum of 8 hours for regular (non-ambient/continuous live) streams, Vimeo allows a maximum of 12 hours, and Twitch allows a maximum of 48 hours.
Refer to the documentation for your streaming platform to confirm requirements and limitations on the stream.