Ah. Well, I consider them an investment. It's either buy old computers now or new computers later (or do without, but that's not really a viable option in today's world).
How long have you been storing them and do you take any precautions? I ask because those batteries have a shelf life and storage condition can change things dramatically. See:
Different ones for different lengths of time. I just go on Craigslist every now and then and when I find a good one nearby I snarf it up. I don't take any particular precautions other than storing them in a climate-controlled part of the house. I'm kinda figuring on having to replace the battery anyway when I bring one from storage into service.