Yeah, a journal is a good way to think about this. These threads are your place to write down your thoughts, stories, share photos, etc. But unlike a journal, most people only fill memory jars with good things. A journal typically includes all your thoughts and worries - This is instead a way of commemorating the happy things that you might otherwise forget about.

In real life, people end the year by emptying the jar and looking back through everything that they saved. Here, "emptying" the jar is just going though your old posts and thinking about this stuff again. We may end up locking the forum (since jars are only used for about one year), but you won't lose access to your post and memories. We'll cross that bridge when we come to it.