Solos and threads can be as long as you want them to be. We do have No Judgements, which are a standard amount given that doesn't require the judge to comment or read much more than a brief scan. Workshops are similar, but they get peer reviewed by the community. Any other judgements will get you commentary by a trained judge who can help remark where you could be stronger.

So yes as long as you want. Standard guidelines for the minimum length are about 10 posts or 5k words. But never worry about writing too much! My solos are always huge

Anything else I can help you with.