Applicable drivers are collected each time the device scans, from there it takes a few hours for it to be processed in the deployment service.  Intune then automatically refreshed the list of drivers daily, and there is a button to sync the driver updates on demand if the last sync time shown is older than you'd like.

So, without using the manual sync button, for healthy scanning devices, should take anywhere from 1/2day to about 1 1/2 days to refresh that list per device.

HTH,
-David