Hi Looney Binns
I think you mean, "How many databases do I need?". The answer is: only one. However, you can create as many tables as you like in that database. MySQL does allow you to create more than one DB, of course, but I can't think of a reason for having more than one for a particular project, unless you're dealing with sensitive info such as addresses or credit details.
I know nothing about archiving scripts, I'm afraid.
HTH
Norm