It would be useful to have more than just the option of choosing priority or not.
A category of "index once and don't index again" would be a very useful status for large read only datasets.
Also having a priority status of high/medium/low would be much more useful.
One more vote for "index once and don't index again" option!
I have a fairly large document archive indexed (over 1 million documents, over 1 Tb data). Rescanning it takes several hours even on a fairly performant PC. Meanwhile, only a fraction of folders in this archive regularly change, most of them are stored as is for years. Ability to ignore them on subsequent scans would speed up thinks a lot.