Most yellow contacts you buy, will be made for occasional wear, since they will be considered theatrical wear. If you do purchase yellow contact lenses that are for everyday use, you will be able to use them for longer periods of time, but you should always check with the manufacturer and/or supplier of the yellow contacts.
If you do purchase yellow contacts for theatrical wear, it is usually recommended that you wear them for no longer than 3 to 4 hours. This gives you enough time for a costume or Halloween party, trick or treating or to take pictures.
After you wear them you should let your eyes rest and properly store and clean the yellow contacts afterwards.
You should typically wait a full 24 hours before you wear your yellow contacts again.