I wonder if humidity could be a factor in why the inks dried. I live in a humid environment so maybe that has kept my inks a little longer. Just a thought. I have some SU pads I bought back in 2003 that still work although some not as strong in color. I hadn't used them for a couple years but kept them stored in a plastic drawer where air still got in. I bought the Inkessentials Ink Refresher spray for these pads. It sort of works, but it's not like reinking and you have to allow time for it to soak in or else your stamping is too wet. It's only a few dollars. It might be worth a try but only a few sprays at time. I use it sometimes because there are some discontinued SU colors that I still like to use.
I do like the new SU pads though. They do have a learning curve, but nice inking.