Depending on any number of things, waterline eyeliner varies in the amount of time it stays on and how it looks through your day. Of course, you are probably much different from everyone else but I will try to provide some guidance.
I like to check my eyes right after I have finished putting on all makeup. Surprising the number of times I realize I need that last swipe with a Q-tip to remove the black fall out from my waterlining under my lower lashes. Also, check for the dreaded “eye boogers”. Sometimes you get a little too much kohl in your eye and it collects at the corners of your eyes. The term is self explanatory. Q tips are great for getting rid of them but don’t sop up too much or your tears when you remove the offensive substances. You don’t wan to dry out. It’s a natural process for your eyes to send out a thickened tear to encapsulate any irritants and shoo them to the corner of your eyes, but it’s not nice to look at. Once you have gotten them out, you are set, they generally don’t come back.
Check to see if the kohl is wearing off over the course of the day. I usually have to reapply mine about once to keep it looking fresh and uniform. You may have to do it more or less times, but check it every time you wash your hands. At work you might want to carry a little container of kohl to keep yourself in the black all day.