One issue is the CPU, the activity of the websites. In the case of the Forum it was excessive. We have a lot of range now, but still, it jumps to 99% very easily. The technical aspect of it is long to explain. Basically we have moments when the activity goes wild. A lot of that has to do with bots and that's something we're working on. Forums attract bots.
As far as file space, we have tons, we're using less than 10%, but that is not the same as Disk Space, which we were at 99% when the system went down, we're now at 58%.
That's where the pictures come in. Large files tend to cause the problem fast. Specially if they are pictures.
I notice on previous posts that one user posted 12 or more very large pictures in separate posts in one afternoon. And that's in one thread, if the same happens in other threads then the Disk space fills up. It can take months, but eventually it will fill up and we'll have the same problem.
Yes, there's the need of doing some house cleaning but it's not easy. It takes time and effort. We could, in theory, go to the files manager and just delete hundreds, or thousands of files at once, without selecting them. But maybe that's not a great idea, some good stuff could be lost.