Well... I wasn't aware of this limitation, but I'm not sure it's that bad. Posts can get VERY long if someone hotlinks 8-10 images. Of course, then someone could argue that having 3 posts for a single topic actually makes the thread longer (physically, on the page) than having a single longer post.
If in doubt, you can always just give the link to the image, as opposed to using the IMG tag to hotlink the image. The mods will discuss this issue, however.