When To String Your Racquet
I get asked this question more than any other and in my opinion there are two answers, both are within you.
Opinion 1: The Pro/Performance/Progressive player
If you are hitting free and clean yet your balls are missing the mark, then it's about time... you should never change your swing to keep the ball in court or indeed work too hard to keep it at good length. Chances are your strings have lost their mojo.
Opinion 2: The Occasional player
If you are an occasional player that, shall we say hits it back to your partner for them to hit it back to you, then a racquet should be re-strung at least twice a year, whether the string breaks or not. A general rule of thumb is; a player should restring as many times in a year as he/she plays in a week. So if you play four times a week, each racquet should be strung at least four times a year. Aggressive, performance-oriented players will likely require more frequent service.
Strings don’t necessarily need to break to indicate time for restringing. Strings can go 'dead' in a frame and remain intact for years. Some players will realise a gradual adverse effect in their game; a good indicator that their strings have 'worn out'!
Opinion 3: Change with the seasons
There is always some trade-off between play-ability and durability from string to string. Usually the better playing strings have shorter life spans than some thicker 15-gauge strings.
“Tighter for control, loose for power” guideline only applies if a player has already achieved some measure of ball control. If a player’s strokes aren't sound and his/her technique isn't working for him/her, nothing will give him/her ball control! For equal amounts of control & power, try stringing your frame in the middle of the recommended tension range for the first string job and adjust accordingly. For a beginner’s frame, string at the loose end of the recommended tension range for a more forgiving string-bed for off-center shots. Once a player is skilled enough to place his/her shots, they may want to re-string at higher tensions to enhance response and increased control.