when to change my string?

[pat666]

Hello all,
I just got my rackets restringed - yonex z force (BG 80 Power, 27 pound) and NS9000 (BG 68 Ti, 27 pound). my questions is how do i know when it is time for me to get new string?
Thanks all

[rattos]

I usually restring them when the string breaks or when the strings are getting hopeless and so bad that you cant hit properly, like when i have troubles hitting to the baseline 4 days in a row

[phili]

When you are no longer satisfied with the racket's performance or when the strings snap :P

[pat666]

thanks all for the replies. I have been doing is that I just used my two thumbs and push the string to see if it is getting loose or not...i think i should stop doing that because i just keep doing it every 5 mins!!!