Are these full-time-studying days or working-while-studying days?
I'm assuming it must be full-time, so…
If you're beast-mode and can study 16 hours a day, that's 96 hours of study time, which would seem reasonable. However, assuming you're more human, studying 8-10 hours a day, that's just 48-60, and even though I'm generally overly-optimistic with people's study plans, I don't feel very optimistic about that one. 😐
I don't recall seeing anyone else study for 6 days and pass for FAR, unless they were just straight out of school (like weeks out of school, not “just a year or two”), though it might have happened and I missed it. I did see someone study for and pass all 4 exams within about a month, but I think FAR had about 10 days out of that month.
If you have a reason you've got to do it in 6 days (NTS expiring, so money's lost either way), go for it – you'll never know till you try. However, if you have the option of moving it later (like 6 days from now is hte last seat this window, but you could wait till next window), I'd strongly recommend waiting. I'm pretty optimistic, but this one's too close for comfort.