How many years can I put on contact lens?

Less than 10 years. If you wear more than this period, contact lens would hurt your ocular surface enviroment, such as lacrimal film, cornea, allergy. So you would always feel itch, red eye, dry eye, blur vision, excretion increase and lacrimation etc. Sometimes you might feel normal even though the contact lens have do harm to you, this is because it would decrease your sensation of your eyes. If you appear those clinical manifestation, go to your ophthalmologist for a advise.