I'd say keep them. If they still work fine then that's what really matters. It's way cheaper (you can't beat free!!) and it's the best eco-choice too. You can always use some liners if they're starting to be not quite as absorbant as they used to be. I even remember one mom sewing some fabric to the center part of her diapers to increase absorbancy (they were quite old and worn, but the elastic was still good). She even sewed cute patterned fabric to the outside and got herself some adorable diapers to boot!

If they start getting really worn before your little one is out of diapers you could always buy a few to supplement your stash. Either now so that what you have gets washed less frequently or later on when you need less diapers anyway...

Karen.