FL Hawk,
The mamasan saying 4 hours is completely useless. Just conning you. If you were experienced you would know you will never get a 4 hour ST unless the girl just happens to be crazy about you.
Some Girls from RB4 try to get away with 30 min quickie STs in the past.
The best you can hope for is 2 hours. Many girls will try to leave after 1 pop.
I never use mamasans to negotiate, it just doesn't help me. Unfortunately masasans are supposed to help the communication but won't give you a good deal. I am firtunate to be able to speak Thai and completely bypass mamasans.
Anyway the girl would not know necessarily what bullshit the mamasan told you.