Yes the vibration for the 3rd eye and opening is done for a period of time. Then you can wait up to a month or continue vibrations.
The openings are done and you continue to meditate on them. But can also include Full Charka meditation if you don't want to wait a month. Remember the openings for opening is one month.
BTW since the 40-day guide is outdated. Aum is vibrated in the Center Anahata green and Yaum is vibrated in the center Ajna indigo chakra. Remember JoS has old, outdated information. Nothing harmful but we've redeveloped.
It's recommended but some people can handle the bioelectrical climb.
Sheer fact is the vibration for the 3rd eye Thoth(Vibrate Th throughout the entire time and round your lips to vibrate the Oh part) or Thaum are the vibrations for the 3rd eye.
We never really delved much into other vibrations on the 3rd eye. We've mentioned before you can vibrate Aum(generic mantra), breathing exercises, feeling exercises(i.e. the odd pressure on your third eye forehead area), and breath in energies.
The reality is simply working on your 3rd eye doesn't work. You need to learn to USE it. So vibrate not just mantras and energy breaths but also focus on feeling the 3rd eye and let it develop.
Early signs are what buddhist call nimitah/nimitas these are gained from mindfulness whereby the person experiences colors and patterns and whatnot while doing basic meditation practice i.e. mindfulness . I suppose calling it nimitas isn't wrong. You'll at some point have colors, images, shapes etc.etc. that is a very good sign. But further work continues. Since we aren't new agers it's just another brick laid down to build up the 3rd eye.
New agers = OMG I saw colors it's a sign. Dude settle down it's just a transient process there's much more to the 3rd eye than simply thinking your tripping balls.
My suggestion is continue using Thaum, use Aum if you want, use thoth if you want, breath/draw energy into the 3rd eye and the other clairvoyant eyes the total of 6: 1/2/3rd/4/5/6.
Seems like your doing a good job. The one month wait is simply to allow your system to get used to it. We suggest it but if you wish to continue on carry on. Try and balance your chakras with a full complete working.
We meditate from Sahasrara down to open up the soul afterwards you can carry from Muladhara up. Also don't forget to vibrate Gaum and silver energy into the pineal gland as you want to work on the pineal. But you can wait a bit for that.