One of my brokers gave me this piece.  I thought it was worth sharing.
Non-accelerated payments are calculated using  12 months worth of payments in a 12 month period. 
 
Accelerated payments are calculated by incorporating 13 months worth of payments in a 12 month period.  The additional month is divided equally among your payment to increase them.
 
Impact of Accelerated Payments
Contractual Amortization   Impact on Amortization
 
40 years                   8 years, 1 month
 
35 years                   6 years, 3 months
 
30 years                   4 years, 10 months
 
25 years                   3 years, 7 months
 
20 years                   2 years, 6 months
 
15 years                   1 year, 8 months
 
10 years                   1 year 
5 years                    5 months
