hmmm, did you read my last post? About using tinypic? I linked you to some details on how to do it, it even has pics explaining the process.
I've been using them for everyday posting of random pics on other forums, so I'm not to sure if they do delete them. I've been using them ever since I posted my first post in my grow journal and they haven't deleted them yet. But yea, that would suck if you go back to your journal and they are gone.
I don't think they have any limitations or rules. Seems like they would have to start deleting some stuff eventually, due to bandwidth and server space.