Well one thing to keep in mind is that, although they all say that they're 198M, it's actually shared memory so the database is only taking 198M *TOTAL* right now. I don't know what you normally see there, but I wouldn't think that 200M is overly large (of course if you normally see that at 10M, maybe it is...)
I think you're correct about losing it's "info over time" if you restart it --I'm pretty sure Oracle does, so I would expect mysql to behave similarly.
Let me know if that helps at all, or if you want any more info and I can try to help you out.
CW