Why can't you wear contact lenses for more than 30 days?

I'm thinking of purchasing some coloured contact lenses to change the colour of my eyes, they won't be prescription contact lenses, however the guidelines say they last 30 days. Obviously there is a reason for this, however after looking around on the internet I can't find the reason - perhaps someone could enlighten me? [:

I think its because contacts can eventually wear out so when you put them on then you cant see as good, i have regular contacts the 2 week ones and i noticed if i keep wearing them more than 2 weeks then my vision is not good anymore hope that helps

The disinfecting stuff can only work for so long before it becomes a possible health hazard- you can get eye infections from bacteria build up. Before you get the contacts, though, you should talk to your eye doctor, since they'll be the most helpful with this type of question. Contacts can also come in different sizes, so you'll have to schedule a fitting with your eye doctor to make sure you get the most comfortable fit.

Hi, on http://www.beautifeye.co.uk they have lenses that last for 90 days. What makes them last longer or shorter time is the water content of the lens. Regards

Monthly lenses go bad and start to rub after 30 days. Annual start to do that in 360 days and so goes on. And why to change you eye color? Brown is the best color!