ideal session length
currently, a session is documented as 20
minutes (i.e. if a device is not seen again after 20 minutes, it is regarded as having "left" the vicinity of the pi) - this is, at best, an educated guess
any consideration regarding the session length should take into account:
- noisy devices that seem to broadcast multiple times in a single minute
- quiet devices that only seem to sporadically broadcast due to some sort of network sleep or doze (esp. Android Marshmallow devices)
further discussion and observation can be added to this issue