The inkjet tankmakers (and I use branded ones) have an evil conspiracy - seems like I've only just put in a new ink tank and bingo! it's running dry. If you're buying a new inkjet printer, then do your internet research and compare the cost per page - it can vary wildly. Printer prices at the lower end of the market here have plummeted in the last few months - clearly, the money's in ink, not hardware...
Anyhoo, I worked out Quite Some Time Ago that the warning on my computer (bells! whistles! all auto-provided from the evil inkjet tankmakers!) that the ink tank was running low and oughta be changed (accompanied by nice graphics of empty tanks) is as premature as Peter crying WOLF when said wolf isn't even a twinkle in daddy or mummy wolf's eyes. Premature is not the word.
So I've taken to waiting till the page actually dies - the ink fades to nuffin on the page and that one page needs reprinting - before I change a black ink tank. And have I had lots more pages between the first (and oft-repeated) warning, and said faded page? OOoooyes. Is it any hassle to reprint that one page after replacing the tank? OOooono.
Colour's a bit trickier, particularly if you have one tank with three colours in it, rather than separate tanks (I think I'd deliberately go that way, next printer). HOWever, the same game applies - you get a bunch more full colour fine and dandy pages before the ink tank starts running dry of one colour and your printouts look odd.
I edit a guild newsletter which involves some colour pages, and I've been finalising the latest issue - which means checking and fixing my goofs and getting a final hard copy to have proofread by others. And it occurred to me, as the colour ink tank began to set off said bells and whistles, that for my purposes, it was irrelevant if the colour page was a bit off - as long as you could read the text, the colour was just an indicator that it was a colour page. And yes, friends, the quality's not 100% but I haven't put in a new tank yet - for what I'm doing, the old one can expire all the way. It's still going.
The other ink-preserving strategy worth trying is printing in draft, by habit, unless you really do need high quality. And maybe even check out what draft is like on your printer and see if it's good enough to be high quality for some of your purposes. These newsletter pages, with shifts and changes and layout fiddling certainly don't need to be anything but draft, and it's a long way off the faded dot-matrix printer draft of earlier computer days. Unless you had a draft page from this printer side by side with a high quality one, I doubt you'd know the difference. It's sharp, black, legible, usable - and involves less ink. Click on Properties in a Windows print window and you'll see draft as one of your options.
When I'm printing photos for scrapbooking or albums or whatever, I think out whether I need to do them at home (eg. to get particular sizes/cropping/greatest control over image) or whether I can be making do with the kiosks at the big stores or other photo-printing services. They charge around 29c per 4in x 6in print - if 4x6 will do the trick, their ink's cheaper to me than my printer's ink (and paper). (I know petrol's involved, but it's usually part of a multi-purpose trip).
On an earlier computer, the printer was connected all the time. It was a laser printer, fairly economical. But did I print stuff? Ooooyes. Emails, and patterns, and all sorts. Nowadays the printer isn't connected all the time. You have to bother to plug it in and power it up. Does less get printed? You'd better believe it. Save stuff electronically and only print if you're feeling like you want to bother is the way of things now. Saves a lot of paper, ink, electricity.