Maildir or mbox?

[Andrey Zhidenkov]

I'm using mutt about 6 month. For this time I have about 5000 messages in my 
mbox
folder. What format is preffered for using with many messages? Is Maildir 
faster? I read
in this mailing list that someone stores his mail in the folder, organized by 
years
and month. I think that is very good idea. Is it very difficult to do that?