system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why my two week disposable contacts need to be disposed of after two weeks?

I take them out every night clean them and put them in solution, and when I have been broke in the past I have used them for up to two months without any discomfort or seeming issues..
gpt
A few different reasons, actually. One, the most prominent, is that your eyes will build up protein deposits on the contacts. The solution you clean them in helps with this, but any solution powerful enough to clean the lens completely is going to be powerful enough to physically break down the lens itself.

Also, soft lenses will begin to change shape over time to fit your eye, which means their ability to adjust your vision degrades. Hard contact lenses do not have this problem, they will actually slightly reshape your eye, but you lose a lot of the comfort and ease of soft lenses.

Contacts are a lot like motor oil in a car. Even if you don't use it, the material that makes it up will eventually just break down and deteriorate over time, but having them in your eye accelerates this process.