I'll have to cop out and give you my standard response to this question, which BTW is a non-answer.
"Because the time they've been allowing guests to enter Pandora has been fluctuating from session to session as it's dependent on several varying factors, I'm not able to advise you on when to line up or if you should line up early. What I can tell you is that opening time has gone from about 60 minutes before the scheduled session start time, to very close to opening time."
If FoP is running as it did yesterday, you could have arrived up to 15 minutes before closing time and still get a FP. If FoP is not behaving and even if you were let in an hour before your time slot, I have seen it where no one got a FoP during the entire session. But too many people are arriving super early, hours too early.
I have an off day today, hey, I deserved a break, so I don't know how it went, but I'll be back tomorrow and will report on how it went today and tomorrow. I'll also be there on your day, but you lucked out, I won't be there until 2:30. If you're still there then and spot a CM who looks clueless, that's me, stop and say hi.