Anyone know how long shelf life is for string's ? I was doing some spring cleaning and found a few packs of RS66 Rotosounds and some Labella hard rockin steel, I had forgot about. They have been in a drawer since 1991. They are all in the original package. They were in the house with central air & heat the whole time, so it was not like they were in a garage or exposed to heat or humidity. Think they are still good ?