Is it true that you can backup the NAV discs for these Pioneer decks? I'm getting that impression from things I've read here.

If that's true, that would be great. I'd feel much more comfortable leaving a copy in the car rather than the original.

Yes

If that's true, that would be great. I'd feel much more comfortable leaving a copy in the car rather than the original.

Why? The disc serves you no purpose in the house.

If you leave a copy at home and the original in the car, in case something happens to the original you still have the copy at home, which you can then copy.

It makes no sense to use the original as a backup.

you would leave a copy in the car because the original is in the house, where your car isnt going to play a role in things if its stolen, broken into. Like for example if someone stole your backpack out of your car with the original disk in it... well your now running on backups now... but if the original is in your house, no problem less a fire, home burglary or the like

It makes no sense to use the original as a backup.

You always use the original as your backup! It's your proof that you've legally purchased the product you are using. Also, it's bound to be your best, most error-free copy, so if the backup gets destroyed you can create a new copy from your original (though this is decidedly less important in the digital age).