Recently flew out of PHL on a late evening flight. Went to check-in at Terminal B, & it looked a zoo. Then found out all F kiosks/counters were unavailable. Went to ask an agent about where to check in for *Gs & was told all F check-ins are closed after 6PM, so I should use a regular line. Are the F check-in counters really closed after 6PM? It's not like the regular lines were "empty", so I can't imagine someone paying for F would enjoy waiting in the regular line!
LAX
To be honest at the B/C ticketing counter, the F line is usually as long if not longer than just waiting for a self serve kiosk. The only benefit tends to be the F counter is better about remembering the priority bag tag.
Just walk up and down a bit and I'm sure you'll find an open kiosk. Just remember to make sure they add your correct bag tag if you're checking something in. You'll end up saving the most time skipping the security lines anyway.