We have been burning through disk space too quickly and the long-term solution is to store the images on Amazon S3 which is basically a "big disk in the cloud". I switched over all new images to be hosted there as of this morning and it seems to be working OK but let me know if any image is not showing up.
Soon I will also migrate the older images over so all the images are in the same spot. This migration takes some time and some images may not load correctly during the migration so I will give a heads-up here first before starting the migration.
The cost of Amazon S3 will bump our overall costs up by a bit but not by much - I think it will be under $10/month. We should be good indefinitely with this set-up, the posts themselves take up very little space so we have hundreds of years worth of space for them now