OP takes up 0,19 KB for the text, plus 5,77 KB for the image
A random flash submittion takes up 64,3 KB
You'd need 10 posts with images to match the space the single flash submittion takes up, and if you don't post with images you'd need just around 300 posts.
Say you post a lot and attach images to your posts every now and then. Even after 2 000 posts, you'd still only take up about 20MB of space; slightly less than MGS: Flash collab DISC 01
If NG desperately needed space, upping the "save" score for the portal, and deleting low view old flashes would be the way to go.