Answer:
Best long term strings around, are Dunlop strings. For about $5 a pack, they last up to two months, and never lose their tone, or tuning. Ernie Balls are good for about a week before they start rusting out. Another good brand is Blue Steals by Dean Markley, which are supposedly cryogenically frozen before being packed and shipped.
The best strings to use for a gig or one time, are Ernie Balls. They rust out quickly and if you buy them from Guitar Center, they sit in the warehouse for god knows how long, before they finally make it to the store, so if you use them, buy from a small shop, because those places get them to you quickest. Guitar Center buys loads of them. Once again though, Dunlop strings haven't let me down yet for a gig, though I change them before I play. I usually keep the new set in for about a month before getting another pack.