I try not to leave my phone plugged in "all the time" - this is the #1 killer of cell phones. Doesn't matter how smart the phone, battery, charger, etc is, charging it all the time shortens the batteries life. Charging it to 100% drastically shortens the life. But that's a different subject.
I use a stand alone GPS as my always on GPS, but I use my phone to navigate to "places". The phone has a much larger and up to date database of places. So I want to find an oil change, or a certain restaurant, or whatever, I ask Google for directions. My phone is fairly new and can run the screen for hours before the battery becomes an issue, so if I need to see the map, I just leave it on. Most of the time the turn by turn audio prompts are enough.
When I drive from one city to another, across 100s of miles, I use the stand alone GPS.
The stand alone gps has a battery in it too, but I don't care about that battery. the stand alone gps is usually turned on when a trip starts and left on until the trip ends.
just my opinions
2013 KZ Sportsmen Classic 200, 20 ft TT
2020 RAM 1500, 5.7 4x4, 8 speed