The five-year-old toner cartridge in my HP 4M started streaking. It was not
low on toner (the Low Toner indicator didn't come on, anyway), and shaking the
cartridge didn't fix the problem.

Although HP's Website says there is no time-limitation on toner-cartridge
warranty (there /is/ one on inkjet-cartridges), I was repeatedly told there
was a one-year warranty.

I escalated the complaint, and somewhat to my surprise, management agreed with
me. I got a new toner cartridge this morning.

Companies vary (and HP tends to treat its customers better than most), but if
you have a good, rational reason that don't like the way you're being
treated -- complain, complain, complain.

PS: HP says it's stopped making toner carts for the 4- and 5-series LaserJets,
tank-like printers made by Canon. If you own and love one of these, you might
want to grab a cartridge.

"'We already know the answers -- we just haven't asked the right questions."
-- Edwin Land