discussion settings: 5 levels…

I’m trying to manage a blog in which there are 5 levels set of discussion. So, there are discussions, replies, replies of replies, and so on……it’s not fair.

So I have thought to:

1) to change settings level to another n (?). What is a good level to set it?

2) to manage old replies with new setting. What should I do to do that? exportation a re-importation of comments?

thanks and ciao ??
Roberto