there was a discussion with an optometrist on this site who quoted many specific issues relating to overnight/extended wear. His conclusion was that under no circumstances should one sleep with one's lenses or wear them for extended periods (i.e. longer than a day) of time otherwise you increase your chances of getting severe eye infections, etc by a factor of 4-5x and if you take occasional mishaps (i.e. sleeping with your lenses in once-in-a-while) out of the equation, that figure increases to a factor 10-15x. You can find this precise information at jnjvisioncare.com and click on acuvue2 and then click on fitting and patient management guide pdf. You will find this information at the very end of that booklet.

[Sorry I can't post any links 'cause the system doesn't allow me to post until i've made my 15th post.]