Hey Joey,
I should clarify!!! The Will Lees are actually SR2000s. They are his custom gauge set though, that's why they're referred to as the Will Lee set. They do say SR2000 Will Lee on the box, and they are the exposed core. So as you say you don't prefer exposed core, stay away from the Will Lee's. So sorry for the confusion!!!!
Regarding your question about the Rotos, I do remember asking the same question about shelf life on them, I was told that by the time they are manufactured, packaged, shipped, received through customs here, distributed to the stores etc, it could be more than 6-7 months by the time you get them on your bass.
I also remember hearing that the warranty on a 4001 is void if Roundwound strings are used on it, hence the reason for the 4003. I don't know if it came from Rick or not but I do remember hearing it in one of the stores at the time.