We recommend getting refills every 2 to 4 weeks. If you wait too long your extensions will fall out and you will require a full set. Factors such as exposure to humidity, steam or touching your eyes a lot may cause the extensions to fall quicker. Refills can take from 45 – 60 minutes, depending on the state of your remaining lashes. A good sign of when you need a refill is when your extensions are 50%-60% gone.