The short answer is no, they don't go bad and if they are indeed the same shingles that are currently on the house, you will be hard pressed to find anything that will be closer in color than that extra bundle. So, check and make sure that they are even the same ones, if they are really from the seventies, chances are that the current roof on your house could be newer than that. In that case there is no sense saving a shingle that no longer belongs to your house. As far as them being stuck together, to some extent, that's possible but most "self seal" shingles have an anti-stick tape on them that keeps the shingles from sticking together in the package, and even if they are tacked together, if you need them in a pinch, it will be well worth the coddling it may take to get them apart.