Last night, I was cleaning out a drawer in one of our bathrooms and found my relatively new package of expensive toric lenses for my left eye (only eye with astigmatism). These lenses are supposed to last for three months each. While we were in Paris, I was running low on lenses and was too lazy (and maybe scared?) to go find an optometrist, have an eye exam, and get fitted again (it took a grueling three visits in the States to find the right lenses for me). So I ended up wearing these lenses for a year each and the ones for my right eye, at least three months each (labeled as one-month disposables).
So after we moved back here, I thought it was time to treat my eyes to new contacts. I confessed to the optometrist that I had worn my present lenses way beyond their expiration date and was shocked to hear from him that it was perfectly fine. One year is fine for 3-month lenses, 3 months is fine for 1-month lenses. So the lens manufacturers are lying to us, in a way, so they can make more money. Don't be fooled -- wear your disposables as long as you comfortably can. When they don't feel right anymore and your vision with them deteriorates, toss'em.