First HM FP I did on my knight was HM LI, I did it before I had even finished my class story, did HM EV too. Time at 50 has nothing to do with it, if you know your class, know the flashpoint and have the proper gear. I was full campaign armor, columi ear, rakata implants, matrix cube, all rakata and bh mods and enhancements, fully augmented, 27 strength hilt and daily hilt. off hand More than enough for HM LI.
I have ran HM LI twice a week since forever on my shadow and on my sawbones. No one kicked me for some reason. I don't care if someone is day 1 50 or day 200 50, gear and knowledge is more important than time.