When should I drop registered users?

I'm just wondering what other Peertube instance owners think about users who request accounts and then after several months, never produce anything?

I have a managed hosted instance which means I have a limit with my storage. I can only take on new users if I have enough storage to offer. For example I only have 5 users currently. I plan on taking on more as soon as I can find the $$$ but my problem is that after 2 months two of the users have yet to log in let alone make a video. So my question is, how long should I wait before I tell them that their accounts will be removed for lack of content? I'm not about paying for users who don't make anything.

So what do you think is a good time to wait? I'm thinking 3 months is more then long enough? What do you think? (Also I'll be adding this to my TOS so that people know when they register.)