-->"CF = Current Fave
ATF = All time Fave
There can be multiple CFs even at a time but I have to assume there can only be one ATF. Right ? (else the term itself is an oxymoron)"
All of that makes perfect sense. However, throughout the strip club forum universe, many (most?) PLs use ATF to mean extra-favorite CF. I do this, too. Partially, I do this to annoy my more anal-retentive brothers, who swear you can only have one ATF :) And partially, I think there's a beautiful self-awareness to how fickle and flighty we all are, ready to drop one ATF and pick up another at the drop of a hat. There's a poetic beauty to having lots of "all time" favorites :)
Anyway! To answer your question:
My CFs (girls who I like enough to set up an appointment with her, but I won't change or cancel my trip if she can't make it) last about 2-6 weeks, after which they've either been promoted to ATF, or dropped.
My ATFs (girls who I like so much, I'll go in just to see her, and might cancel my trip if she can't work) tend to last 6 months to 2 years, with a few lasting much longer than that