Join or not

I'm new to uploading my work to 3D sites. Should I join all the items in a model together or is it preferable to leave them individual. I just finished a model that has almost 300 parts and it feels wrong to upload it like that.

I would say it greatly depends on the situation. Most of the time the most possible detail and separation is the right thing to do, since it is much easier to collapse everything into a single object than separate everything after all.