Probably More than 30 mins. or when you go to sleep at night. I've herd you should avoid sunlight though.
You can keep aloe vera on your face for 15-20 minutes before rinsing it off with lukewarm water. It is gentle enough to be left on overnight for extra hydration, but some people may experience skin irritation with prolonged use. Be sure to do a patch test first to see how your skin reacts.
30 mints
You can't really use too much aloe - just apply as needed for relief.
Keep it clean, covered and protected. Unless larger than the palm of the victim's hand, or placed somewhere sensitive(face, joints, genitals) it can then be left to heal on its own. Keep blisters intact for as long as possible.
Do not put milk on a sunburn. Get a sunburn treatment with aloe vera and lidocaine. Drink the milk.
Aloe makes hair healthy and it grows 1/2 inch a month
However long as you want it to be there. ;D
It is not suggested that Aloe Vera juice be frozen since it can deplete nutrients and dilute it. If it needs to be kept longer, it should be refrigerated, but not for too long due to gradual nutrient loss.
You should keep it in for as long as the dentist that fitted it advises.
Three to four months in tropical and sub-tropical conditions
Leftovers should be kept for no more than 3-4 days according to the "how long to keep leftovers chart."
as long as you can keep it