Stored indoors or at least out of the sun, heat, and rain? If so, you're probably good to use them all up. If stored in a situation where a cat might not fare so well, then they might have prematurely met their demise. No harm in testing with them and seeing if the results make sense. TFT sells a refills kit that doesn't make you pay for the box/hardware so you can save a little there if/when you refill some/all be sure to see if a whole set is cheaper than just the ones you need. Since you have vinyl - as long as your fill water isn't calcium ridiculous you could even ask them to skip the calcium and give you a little extra of something you use. Can't promise anything, not affiliated with tftkits.