According to Goin Postal, placing two 44-cent stamps on a letter does not speed up the delivery time. The U.S. Post Office simply processes the letter according to first class postage procedures, and it arrives at the destination within one to three business days, on average.
Instead of spending extra money on two first-class stamps per letter, a person can opt to send a letter via Priority Mail. According to the U.S. Post Office, Priority Mail is delivered to its destination within three days, and Priority Mail Express offers guaranteed overnight delivery. Additional fees are charged to have Priority Mail delivered on a Sunday or holiday.