It depends on what kinds of eye drops you use, if you only use the eye drops full of oxygen thus to refresh you in the morning there would be unharmful to your eyes. But if you use some prescription eye drops especially for special eye diseases, that would be harmful.
Most the eye drops not only have the function to treat some eye problems, but also they contain some anticorrosive ingredient. If you use them frequently, the anticorrosive ingredient will damage the structure of ocular surface and cause irritation. So you can use a small amount of eye drops when your eyes get tired to relieve the eye fatigue. Eye drops can not be prolonged use.