@eltr,

I have been using Garmin products since 2012 and still have the same SD card in them.

Never have reformed any of the SD cards.

That goes for 7 different units I use.

The hiking Units have had maps deleted many times on the SD cards.
I have add small topo maps and larger topo maps to all the units and have never run into any type of problem reading any of the map.

This is also true for all the LMT units I have.

When using Garmin Express they are very hard on removal and install on both the internal and Sd cards and never have run into problems.

Maybe I am lucky about this.