I’d suggest that people pay for interview prep even without a scheduled interview. I wouldn’t want to find out that I don’t interview well with one already scheduled. If you find out that you are rough around the edges, then use it as training. Go multiple times, use different prep services, and learn to interview well if needed. It would also help to be ready should something come up quickly. That is in addition to reading every interview book that you can find and practicing over and over with friends and family. There is too much on the line to expect a thick logbook to carry any weight. Lots of people have thick logbooks. Being experienced with the interview process and able to comfortably sell yourself to those sitting across the table could really pay off. There is still no guarantee, but I’d rather get shot down knowing that I gave it my absolute best, than wish that I had done more to prepare.