I am hard to freak out when it comes to your mantras. You know by now that I am pretty big on combining Thai Massage work with energy concepts. Mantras really help channel intention and energy flow. I have used such things myself frequently.
Regarding session length, once you get good at this, it is very easy to do very long sessions. I think the longest session I ever did was 3.5 hours. My average sessions were generally between 2 and 2.5 hours. I never offered Thai Massage sessions less than 2 hours, and nobody ever even requested a shorter session from me. I simply told my clients that a session is 2 hours, and that was it.
I am glad to hear that it all connects for you and that you are in the flow of it. That's the goal of it - not just memorizing tons of techniques. That might be necessary in the beginning, but if it doesn't go beyond that, Thai Massage will never unfold its true potential. Clearly that's where you are now. Congratulations!