I just created my girl account recently...
I'll probably maintain both of them indefinitely. My past doesn't scare me.
Eventually my male-presenting account will transition into a female-presenting one that isn't mostly about trans issues. Maybe they'll merge completely, who knows. I will link them eventually, and friends can be on either or both.
The hardest part is being unable to keep them both open at the same time (which is mainly a problem at work where private browsing is disabled). I wish FB allowed multiple joined accounts the way Google does.