I never archive on my personal Gmail account. Right now I have ~16K read emails, completely unstructured. But it doesn't matter too much because emails I get there rarely need responding to, and I normally get around 5-6 emails a day to that address so I can read them all easily.

My work account however is organised into folders, I normally just leave items as unread until I've replied or am finished with them, then they're archived into folders.