Hi!
You sound like a stronger candidate than myself! I'm also applying to Quantitative marketing, 13 schools(wharton, hbs, sloan, kellogg, stanford, stern, columbia, u mich, yale, cornell, ucla, haas, and u. chicago).
I'm finishing up with 3 left. hoping to wrap up this weekend. But yes, I agree with you. It is taking a tremendous amount of time! I took the week off during thanksgiving doing preparations for applications(registering, looking at requirements, making package for recommenders, etc...), and writing preliminary SOPs. Then I took all of x-mas/new year week doing the bulk of applications
my background:
GRE: 800 q, 740 a, 530 v(non native english speaker)
GMAT: 690(again, non-native, i'm using my GRE)
B.S. in EE/CS from top tier university(lack laster GPA)
founded my own company while in college, worked 2 years
my only selling point is that I've had RA-ships with top marketing professors this year, and I've had contact with a number of them.
Good luck all!