SYMPTOM
Environment reporting using Strategy Enterprise Manager shows a high number of mobile sessions that are opened and closed instantaneously within very short time for one or more mobile users.
In below example, statistics logged for one Mobile user are shown (EVENTSOURCE = 29 stands for Mobile sessions). Session life time is null.

CAUSE
These sessions are logged for each login attempt after a governing limit on Intelligence Server is hit, e.g. Maximum Number of Interactive Sessions. Thereby, no session is established, however the session creation attempt is still logged into statistics.
ACTION
This behavior is by design and no reason for concern.