Okay, I thought I understood Garmin maps pretty good but you've got me confused, Terry. Are you saying it should work or it shouldn't?
I see no reason it shouldn't work. Mapsource doesn't care what device a map product was originally unlocked to. Once a map product is installed in Mapsource you can add as many unlock codes to that product as you wish to buy. I've got one with three unlock codes .. one for my Nuvi, one for my eTrex and one for Mobile PC. Mapsource is happy. The Nuvi is happy. The eTrex is happy. Mobile PC is happy. I'm happy.
So, with each new lifetime update download for the Nuvi, Brad would be able to buy an unlock code for the 20x, add it to Mapsource and compile the maps for Mobile PC rather than doing another download for Mobile PC.
But I'm pretty sure that's not what Brad wants.
The real issue is the lifetime thing. If Brad doesn't want to have to buy a new unlock code for Mobile PC for each update and doesn't want to have to download each update twice, it should still work. When I go to My Garmin and go to the MyMaps tab and click on Details for my City Navigator lifetime update product, it lists the unlock code for each update that I've received. So, all Brad should have to do is cut/paste the unlock code for the City Navigator lifetime update version that is registered to his 20x into Mapsource and he's good to go (this requires purchasing another lifetime update for his 20x, which he said he's prepared to do).
The tricky part is, When does the unlock code for each quarterly update get placed in MyGarmin? Does it go there as soon as he is notified of an update available? Or does he have to start the download to trigger it. Either way, I'm positive that what Brad wants to do will work. The worst case is that he would have to start the download to trigger the creation of the unlock code, kill the download, go to his MyGarmin and cut/paste the unlock code into Mapsource.
...ken...