For agency girls, my guess would be the girls during the period t1, t2, where t1= 2 years after she starts working and t2 = the minimum between 6 years after she start working and the time she turns 30 (or starts looking as if she is over 30). Of course, I make an assumption that she is good, reasonably likes her job, is willing to work full-time and learn during the process, and does not make any comments on TERB that may turn clients away from her (i.e., good at pretending and shutting up when it affects $$$).
For independents: I have no idea. I do not use them as most of them are too opinionated and are not shy showing it + have too much of self-esteem (and, again, are not too shy in showing ot). I am all for strong and independent women, but, IMHO, in this profession they must pretend that they are innocent and naive
. (again, I am talking about the average demand and it is IMHO)