sanyo pm 8200 will hold? or any cell phone in general? Will it ever fill up so there is no room left for new messages?If it will fill up how many messages will it hold before the phone company doesn't allow anymore voicemails??

I can't give you an exact number of messages but I can tell you that your mailbox will fill up eventually and then no one will be able to leave you a message.

Yep, chris was right, Vmail is not stored in your cellphone, its at your service provider server whereby most can only keep 10 vmail up to 7 days. After that it'll be deleted automatically.