i actually finished my MA iduring the first semester of my PhD program. i had no choice because my admission was contingent on me completing my MA degree. they allowed me to start my phd coursework even though i didn't finish, but i had to finish by the end of the first semester.
knowing this, i took a lot of time at the end of summer/beginning of the semester and finished by the beginning of october . it was "easier" that i only took 2 graduate seminars and then a language class. i also worked hard on it during the beginning of the semester because my coursework load was lighter and i knew it would alll just pile up. the phrase "a good thesis is a done thesis" is one that helped me a lot with as well. my MA committee knew my situation and worked with me to get everything done as quickly as possible. i got through it by chipping away at it. since i had no choice in doing it, it definitely lit a fire under my ass.
i definitely approached it knowing i was not a machine and had to balance my time more. i would also recommend to anyone, knowing what i know now, to do you best to work on it during the summer just because it IS difficult to do it during PhD time, but that if you had to then be disciplined (but not necessarily a machine).
whatever you decide, good luck!