At least once a day. It depends on how much sleep I get, if I am reading or on the computer too much, or if I am dealing with cold or wind. Usually I use Refresh two or three times a day. If I need to, I will use it two or three times an hour. You can use Refresh as often as you like. If your eyes are feeling dry and tired, put a drop in each eye. If they are really sore, you can flood the eye to get relief. Also, when it's sunny, I wear a good pair of fit-over sunglasses that also block light from the sides for protection. If any eye drop is irritating your eye, it's because of the preservative in the eye drop. Both of my eyes get dry because of medications I am taking. My left eye is typically more dry and irritated because of my eye medications. I try to keep this eye well lubricated.

Your situation might be different. I am dealing with dry mouth also. My dry eye issues might be worse for me than what you are experiencing. You will just have to experiment to see what works. If I am having an allergic reaction to my glaucoma drops, I will use GenTeal Gel for dry eyes. I think the Refresh gel drops would work too. Gel drops are thicker than normal artificial tears, so I generally use them at night just before I go to bed.