I've seen as little as a week recommended and that sounds reasonable if they're not thick. If you have them in a larger bundle the inner ones may be a bit damp still. Theres no real set timeline, just when the outer paper feels dry and crumbly (like storebought garlic) they are ready to go.

I start selling mine as fresh garlic as soon as dug then wait a couple of weeks before cleaning and grading the majority. I like it nicely dried befor packing it in pecks and larger containers. I have found that hanging in bunches of 12 works best, for me, tried larger bunches up to 25 but it didn't dry down as well nor as fast.