I have mine set for two minutes right before lights go on and off. I also have a one minute for mid day and a couple of 15 second mistings in the night, for just a subtle humidity boost.
Very much a variable question. Depends on a lot of things. Type of chameleon, type of enclosure, your natural humidity levels, etc. those care guides given are definitely a good start.
Gonna depend on your ambient conditions and type of enclosure set up. Bio active set up in a hybrid enclosure in a humid part of the country you would not run longer misting sessions. If you have high humidity you remove the morning misting as it can build your humidity too much. Say you live somewhere like AZ with low humidity and have screen or hybrid your misting sessions are going to be longer. Even with bioactive in a dry climate you may still need to run longer morning and evening mistings. Your misting length is also going to depend on your set up and ambient conditions. Rule of thumb for most is mist morning about 15-30 minutes after lights on and a few hours before lights off. But you have to tailor that to your set up and environment.