[otrs] When to start archiving tickets?

We've been using OTRS for about six month now (9,000 tickets, 62,000 articles) and I'm starting to notice sluggishness. I've tried switching from IIS + PerlEx to Apache + mod_perl but that hasn't made a noticeable difference. My next move is to investigate archiving. Has anyone else had a similar experience? When did others start archiving? What effect did it have? Are there other more obvious places to look next? I've read the tuning guide but it seems like we're pretty small by those standards. http://doc.otrs.org/3.0/en/html/performance-tuning.html Hugh