Kind of OT: if you want to see what should be available at your location, check out tvfool.com. They have a tool that lets you enter a location (address or long/lat) and based on the topography and propagation models it predicts what broadcast stations you can get and how strong they will be, and whether for each you will need a simple indoor antenna, an attic antenna, or a roof antenna.
Unfortunately, tvfool is no longer being maintained and doesn't show correct information for post repack channels. An up to date replacement is here.
I'm amazed that this is only the first time since the introduction of ATSC. "Rescanning" your TV is something that happens once every couple of years or so in the UK, to pick up new channels or update changed ones.
It's the second time. First time was in 2009 when the 700 MHz band (channels 52 through 69) was reallocated to mobile.
It happens pretty frequently(well, maybe every couple months) on an individual channel basis for me; I think this is just referring to the fact a whole lot of channels will be shifting frequencies at once.
It happens routinely in the US. It is a major PITA because you can end up losing marginal stations in the process since TV manufacturers can't find a way to preserve existing channels after a rescan.
Not necessarily related but I'm a bit disappointed in the lack of ATSC 3.0 tuners available (are there any?) in US. Phoenix is a test market and I can't even find a tuner to test.