1. Yes - they despawn every 12 hours (12 real-life years).
2. Yup - you can find a list of most of the locations
here.
3. Try to learn your way around the Glass Desert and find the locations along the way. I too struggle with directions - but after charging around at 11:59 in-game AM in search for gilded ginger, I know it like the back of my hand.
Good luck!