Navigation disc running

I have a 2010 Avalanche with factory navigation system, I can go open the door after the truck has been sitting for a couple of days and I can hear the navigation disc whirring occasionally. It doesn't seem to run the battery down and the system works as it should, do they all run all the time?

My 03 does it if I leave the disk in it. I usually take it out so it does not get scratched up.

Any time you "trigger" an action with the vehicle (opening a door, bumping a button, moving the seat, etc) it begins a navigation preload process.

I agree with above anytime you hit a remote button or open door etc. with a disc in it will start up to be ready when you start the motor. It will also run for the time until the shut down electronics of the AV (forgot exact minutes 5 or so I think) then it shuts off when the radio and other devices do. I have learned that through many hours of sitting in  my AV in parking lot waiting for family members to return to the AV.

Ok, thanks for the answers, I guess it's normal so I won't worry about it.