I've been using Brother laser printers for about 10 years. Back in 2004 I had a 1440 that averaged over 3,000 pages on a TN450 cartridge. I replaced that with a 5240 that averaged about 2,400 pages per cartridge. Now I have a 2270DW that's averaging 1,200 pages. Is there some explanation for this reduced yield? Thanks! ...Steve