i tend to keep my mail box pruned, but still keep nearly ½ of all the messages; i archive once every 6 months or so. mailbox gets big, but i've not had any problems. e.g:
cpu% grep 'Well as much as I love how upas' /mail/fs/mbox/*/body /mail/fs/mbox/2634/body:Well as much as I love how upas/fs works, it, along with Acme's Mail /mail/fs/mbox/2638/body:> Well as much as I love how upas/fs works, it, along with Acme's Mail /mail/fs/mbox/2640/body:> Well as much as I love how upas/fs works, it, along with Acme's Mail have you found a upas limit? >> Well as much as I love how upas/fs works, it, along with Acme's Mail >> program, probably wouldn't be able to handle the amount of email I get >> or let me organize it the way I can with my Mac and Mail.app or even >> "mutt". > > I just have 9fans and some private email on my gmx-account (which I use with > acme Mail and upas/fs) - I must say that rocks. I don't know what you mean by > 'organizing', tho - several mailinglists? html-mail users?
