I have a bit of that myself Dave, I think everyone does.
I make a point of unsubscribing from spam, a lot of the time the businesses are using email marketing software and it really does unsubscribe you. If it keeps coming through, that is when I start marking as spam to train the spam filters.
The maintenance I was referring to was more about tidying up the email lists that I have genuinely subscribed to. For example, I'm signed up to a number of deal sites - they email me regularly & I read them from time to time but I don't want them choking up my primary inbox, so I move them all to a folder.
I've got that same basic principle setup for a raft of different categories of email I receive from all over the place, just to make reading more important mail easier - so I'm not having to manually filter through the constant stream of email myself.
How do you handle it?