when to cleanup imap folders?

[fvgi242ss]

I run cyrus 2.1.18-2ubuntu (dapper) and it stores about 300.000 mails.
Performance in kmail and squirrelmail is great and everything works
as expected.

is there a recommendation to cleanup mails in order not to run into
trouble with the filesystem?

i want to hold as many mails as possible because its a great way to search
for solutions.

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