[Dovecot] Maildir and counting inodes

I've been testing with alpha 3 and I am about ready to go production. I am switching from mbox to maildir and I'd like to know if there is a formula or rule of thumb for determining if your file system will have enough inodes to handle all the mail message files.

I could write a script to look at each user's mbox files, count the number messages and calculate the average number of emails per user, then add a fudge factor for expected growth. However, I doubt anybody actually goes to this much trouble to plan ahead. Or do they?

I'm running Solaris 9 and when I created the file system I just used the defaults. If I need to change anything, I'd rather do it before going production. Thanks for any info you can provide on this subject.