The time required is one day. I believe you can fly back to her when PH resets at 12 AM (midnight) PST and complete that days quest and start the next one. Of course then you have to wait for midnight again. So I'd just do a quest every day during your normal play time like most people do with Vidia's spin.
You just need some pixie patience and you'll have those badges, plus if you aren't leveled up it also gives you points.
