Letting your mascara dry in between coats can be a recipe for disaster. What usually ends up happening is that your lashes get dry, crunchy and are no longer moldable. It’s okay to give them a minute or so in between coats but you don’t want to wait much longer than that. What I usually do is do one eye, move to the other and then back to the first one. I keep up this sequence until I get the look I want.