Thank you both,
I'm just thinking I could have more time for revision if I take november's exam. I have already taken GRE math last year, I got 780[~79%] and now I am aiming higher, although I don't know if this is necessary for my applications.
If you know, are these dates http://www.ets.org/gre/subject/scores/get
[my deadlines are January 1st]