I've got 4 FGII
ICC screens (one is in the car, but I've recently done a lot with the other 3)... The flash memory chip in these things seems to be really bad, all 3 report ECC errors (EEC = error correcting code) when reading the file system files. And I mean, an absolute s-load of them, you would not believe it. The ECC software routines fix the errors (apparently up to 4 bits per page - with logic to always tell if 5 bits are wrong - 6 or more and it'll "probably" be able to tell - but over 4 and it can no longer fix the data).
These chips are rated at 10 years data retention. All of the good ones back in 2011 were rated this way. NASA has a pdf (I found) that tests Samsung flash chips (these are some of the best, not that I rate Samsung for anything else), using 125c temperatures and 0, 100 & 500 hour tests - at 100 hours, one bit had failed and the guy noted that's a lot less than 10 years. His recommendation was ECC was very important if they were to use these things.
These units also have a "cold-power-up" counter that I've found, my original unit is now at over 500 due to all the tests I've run. I'm not sure simply disconnecting/reconnecting power is an issue, but maybe a fully charged battery is (I'm using a properly configured 12v supply and a brand new battery can be over 14v).
Personally, I now just think many just end up getting that 5th bit lost and the unit no longer works. Time is a real killer, isn't it.
(Oh, and I'm having real trouble finding V23-V25 .fbl files online to test out the Sat-Nav to see if I can update the maps.)