This decision should be made by your eye doctor.  He/she will recommend a contact lens replacement schedule for you based on four factors:

1.      The type of contact lenses prescribed for you.

2.      How long and how often you wear your lenses.

3.      How quickly your contact lenses get dirty.

4.      How well your eyes can tolerate contact lens wear.

Everyone's eyes are different.  Some people can easily tolerate contact lens wear, but others cannot.  Some contact lens wearers can wear extended wear lenses safely and comfortably overnight.  Others can only wear them on a daily wear basis.  And some people can only wear contact lenses for a few hours at a time.

The only way to determine the appropriate replacement frequency for your contact lenses is to have a professional contact lens fitting and a number of follow-up exams by your eye doctor.  He/she will examine your eyes after you've worn contact lenses for a specified period of time.  Based on the appearance of your eyes and your lenses (and your comfort level) at these follow-up exams, your doctor will be able to determine how long and how often you can safely wear contact lenses and how frequently you should replace them.

One thing all eye doctors agree on when it comes to contact lens wear:  "When in doubt, throw them out."  In other words, if your lenses begin to feel uncomfortable or your vision doesn't seem as clear as it should be, remove and discard your lenses and replace them with a fresh pair.  If problems persist, remove the new contact lenses and see your eye doctor immediately.