I have this Wilson racquet with some unknown strings (got it as a gift so I don't know). I've been playing with the same thing for about 3 years, and I don't know If I need to be getting new strings or not. When I try do some of the spins, the strings tend to warp and bend out of the pattern, so I just move them back with my hand. Is it time to get some new strings? How close are those to being dead? And, how do I test to see if strings are still good (tension etc.) ? Thanks.