Proper prepping increases retention. I used to have customers nail popping off a few days or week later. When I changed the products I was using and improved my technique, all of the pop offs went away. Now my clients nails stay on for several weeks. Some people would wait 5 wks for a fill in but I had to set some rules in place. Because that is more work on you and will also lead to breaks in the apex area. I recommend getting fills every 3-4 weeks, depending on how fast their nails grow.