LH F on a 744 is great when traveling with a partner. If traveling solo, UA F Suite is a far better experience.

LH F terminal is a great perk if originating/departing from FRA in F class. LH F terminal provides little benefit to the connecting FRA passenger. It's just a lounge afterall. One would have to be an extreme airline fanatic to intentionally schedule a connection in FRA or opt for a longer connection in FRA just for a lounge.