At what point will you stop using F/U on your main and turn to only slave accounts?
It depends on the niche, the audience, the engagement rate and of course, your goals.
some say stop f/uf at 20K, some at 40K and some at 100K, but every account works different.
Let’s say if you stop f/uf at 20-30K and you have 3-6% engagement rate just from posting and slaves - I believe you’re good to go
It’s all up to your own judgement past ~20k, if you feel that your account is at risk of getting banned (PVA, action blocks, etc), then the sooner the better. The general rule of thumb is that you should stop f/uf when your acc can grow by just the quality of your posts.