Considering that the FRA flight departs in the middle of the night, I usually check in very, very late. (65 min prior to departure or so)
With the usual crowds both at immigration and security, I get to the gate 20 minutes prior to departure. That does not leave much time for the lounge.
The biggest advantage is that the lounge is directly beside of the departure gate. As others mentioned, the F-Section has Lanson champagne.