6-8 yr old rema tiptop patches- too old?

Just got back to riding after 6 months off and had a couple of problems with patches. Using the usual abrade/clean - alky or acetone then lay down the glue, wait to dry , apply patch and wait a bit. Tried several and had the patch peel away under a bit of stretching of the tube. thought there might be something amiss with the adhesive and the result with the different brand of valcanising fluid was the same. The patches themselves were not sticking to the alum base sheet and the plastic was intact on the peel way.They felt as flexible as new so I don't think the patches themselves were bad but I can't speak to the cold vulcanzing agent that's supposed to be activated by the fluid in the tube Going to buy a couple patch kits before I commit to another couple boxes of rema small/large patches. Again 6-8 yr old patches out of the box (stored at ambient temps SoCal- hottish summers but the restf the yr pretty mild - coastal). Thoughts?? Thanks Pat