I just wanted to post this for others who may not be aware of this great policy. I was there twice last week and didn't realize I could have skipped the long line the 2nd time. I hope this helps someone else.
From the TKTS website:
"TKTS patrons may return to the iconic discount ticket booth within 7 days of their TKTS purchase and walk up to window #1 with their TKTS ticket stub, thereby avoiding the longer lines at peak hours. Thus, allowing them quicker access to purchase same-day discounts or future-performance full-priced tickets"
"All you have to do is bring your ticket stub to Window #1, within seven days of that ticket’s date, and you may purchase full- or discount-priced tickets to the available Broadway or Off Broadway shows of your choice. TDF feels that this will help visitors who are in town for a limited period of time enjoy more theatre during their trip and save a some of their time for more sightseeing."