Please stop reporting all OF models as spam. If a post is off-topic, report is as off-topic. If community rules forbid OF models from posting, report that. If a user is flooding a sub with multiple posts a day in a row, that’s a legit report as well.
Otherwise a post by an OF model is not in and of itself spam, even if it is made by a <ferengi>female</ferengi> with the temerity to control her own sexuality.
Reducing posting frequency is a great solution.
I think only once per week is a bit extreme, but something like, once per sub per day, and cannot share the same photo in the same sub again until somewhere between 1-6 months have passed.