My experience has been that schedulers push hard to get shops done well before both Thanksgiving and Christmas. You'll see bonuses by the second week of December.
If data points interest you, I can offer my experience:
2010 monthly average: $2,053/mo in fees and $1,174/mo in reimbursements.
November 2010: $1,582 in fees and $779 in reimbursements.
December 2010: $583.50 in fees and $1,218 in reimbursements.
In 2011 I simplified my tracking. Here's the net of payments I received from MSC less out of pocket expenses. Since I was tracking payments received instead of fees earned, I'll list January 2012 since most of what I earned in December 2011 would have been paid in January 2012:
November 2011: $999
December 2011: $1,230
January 2012: $349
December has consistently been one of the slowest months of the year for me.
Shopping since 1995; full-time since 2009. Blogging about shopping on www.myfrugalmiser.com.