Standard off-the-shelf moisturizing drops, like Visine, say to not use more than 4 times a day.
The answer to this depends on your definition of “bad” and what specific drop is being used.
Is a strict artificial tear drop unhealthy? No. Often used in dry eye management, an artificial tear is essentially an adjunct for your own natural tears designed to either supplement your own production or promote stability of the tears you do produce. One of the downsides is that some of the thicker formulations can get a bit messy or temporarily blur your vision. Artificial tears that have preservatives have a greater tendency to irritate the eyes over time than preservative-free ones.
Visine, Clear Eyes, or other drops with active ingredients designed to constrict blood vessels are another story. These drops have much greater potential for toxic effects with prolonged use and can also mask underlying problems. Thus the recommendation not to use beyond a few days without seeking medical attention.
