These are some contacts you can barely feels. They're the most lightweight and comforatable out of the three kinds I've worn.
They're designed to be worn straight through up to a month. I'd suggest taking them out one night every week or so to avoid occasionl morning discomfort. I'd also suggest you not wear them any longer than two months...
If you're like me then you like to make things last as long as possible. Contact lenses will usually last at least twice as long and the doctor tells you to wear them. I once wore the same pare of PureVision for about three months. It was uncomfortable and they stopped working so well. But if you want, you can wear these contacts for six or seven weeks with no problem.
Untinted contacts are a must if you work and/or drive a lot at night. Having the untinted kind improved my normal night vision immensely, and improved my nightime driving vision by about 200% (a very, very, important thing).
These are the most comfortable contacts I've ever worn. Not to sound cliche, but...I highly recommend them!