I'm sure there's some reason my eye doc says to wear them only for 4-6 weeks then crack open a new pair, but as far as I'm concerned, I'm not going to toss a pair in the garbage that feels no different after 3 months of use than they did the day I opened them.
lease don't do this.
Basically -- a lot of scientists spent a great deal of time developing special plastics which let a good amount of oxygen through into the eye. Now the only problem is that the protein that floats around in your eyes starts to bind to the plastic of the contact lens, and, over time, less and less oxygen goes through the contact lens.
Since the cells of the eye require oxygen to live, the cells signal the body to start growing blood vessels. Unfortunately, blood vessels are not transparent, so if this gets way out of hand, you can go blind. (Corneal Neovascularization)
You only get one set of eyes, please don't ruin them over $60. If you really can't afford it, consider glasses.