I can take a while, I think depending on which officer that takes your case. I've been waiting over 4 months for my LTR. All requirements met. The latest status says "Final Review" and it has been stuck there for over two months. I have received no response to several e-mails, and when calling I only get to the operator who checks the case # and then tells me to keep waiting. Keeping my thumbs that it will go through eventually. Some friends of mine (less qualified in comparison) had a very responsive officer and received their LTR endorsement letter in less than 4 weeks.