I've been routinely receiving junk mail for a person that I know for a fact has been dead for about a decade. I used to do this with that mail, but stopped a couple of years ago. Now I just toss it directly in the recycling bin.
They didn't pay you anything to wade through their junk. You aren't their slave unless you sign.
And I don't open the mail -- that's a crime the postal service would take very seriously indeed. Sure, perhaps my practice is technically illegal, but I don't think it's the sort of illegal that the USPS would spend a lot of time and money on.
I'm not opening someone else's mail, I'm not preventing it from being delivered to the address on it, and I'm not preventing the recipient from receiving it. His death does that.