When does a device's home_residing_cbg change?

I’m interested in looking at home residing devices to study specific events. Suppose a conference occurs in ABC, Pennsylvania. I want to see which home CBG’s from other parts of the country visited a location via the visit_by_cbg column. My questions are:

  1. How long does a device need to reside in a CBG for it to become the CBG that it’s visiting from? ​
  2. Is this even possible?
  3. If this isn’t possible, would it be possible to make a request for a specific product to know visitors from CBG’s to other POI’s from out of state CBG’s?