I'm with DonnaC on this one. I have a knitted afghan that is at least 20 years old, gets used almost daily by me as well as at least daily by the dogs. It's in perfect shape (except for the need for washing at the moment!). I'm not sure how much more 'preserving' really needs to be done to a crocheted afghan. I've seen them many decades old holding up just fine. In fact, the only reason I've ever gotten rid of any is because I hate the colors any longer.