V-tech Racquet Solutions 

The general rule of thumb is to restring as many times per year as number of times you play per week.  For instance, if you play three times a week, you should restring three time a year. 

However, this is a very general rule of thumb and it does not take into account the player's style of play, type of strings, string gauge, type of racquet, and tension.  For instance, many types of polyester strings go "dead" after 10-12 hours of medium to hard play and some brands will go dead even sooner.  So if you play three times a week for 2 hours per day, you can easily rack up 10-12 hours in little over a week.  Hence, if you restring only once a year you will be playing with relatively poorly performing strings most of the time.

In contrast, a natural gut although "fragile" than most strings plays almost as good as new up until they break (just as long the strings does not get wet or left in the car on a hot day).  Therefore, it may be conceivable that you can enjoy a set of natural gut for a whole year without the need to restring your racquet. 

The short answer would be...YES!  In general, a higher quality stringing machine will help lead to a higher quality string job.  High quality stringing machines include electronic controlled constant pull tensioning systems, or stand-up professional lock-out systems.

However, although the machine is important, it is only one part of the equation to a quality string job.  The other important part is...the STRINGER performing the job.  The stringer must use the equipment correctly and perform the stringing using best practice techniques as described by the USRSA. 

Overall, while the equipment is important, the experience and skill of the stringer is equally important, if not more so.  When choosing a stringer, USRSA recommends that you seek out a Master Racquet Technician (MRT) or Certified Stringer (CS). 

Initially, you have to realize that part of it is because of high level competitive tennis, particularly in today's modern heavy topspin, power baseline game.  So if your style of play is similar to what I described, be prepared to break strings more often than recreational players or younger players that still lack the strength to hit a hard, topspin ball.  Nonetheless, there are common approaches that you could try to make your strings last longer, as follows:

1. Use a thicker guage of the same string, if available.
2. Use a different, more durable type of string.  For example, switch to a polyester string or a hybrid with polyester mains and a softer string in the crosses.
3. Reduce the tension that you string at.
4. Change to a different brand of string.  Some brand strings are known to be more durable for the same type of string as other brands.
5. Use string savers.

The biggest misconception about racquet strings is that the players think the string will make a big difference in their game in terms of how the "spin" goes, but even though it is the case it is acheived in a different way.  The strings will allow you to hit a little bit harder and that is what is going to give you spin.  The strings themselves are not responsible for spin as the spin is the function of your swing.

Power pads have three primary functions.

 1) Vibration dampening. The pad absorbs shock. Given that there are so many vibration dampeners on the market, power pads are no longer necessary as vibration dampeners. However, you might consider adding them to a racquet where a vibration dampener is already in use and you want additional dampening.

 2) Longer strings. The power pads slightly extend the length of the strings they effect. Longer strings are believed to store (and thus transfer more) energy to the ball. The effect of this is so minimal that I don't think it matters.

 3) Durability. On some old racquets, the pads eliminate a less than optimal angle of the string as it goes into the grommet hole. This is why we see power pads used on wood racquets. Modern grommet systems, frame shapes, and whole layouts are set-up not to need pads.

 If power pads were still necessary, manufacturers would use them. So now it's more of a preference. The only conceivable use I can imagine on a modern grommet system is a situation where either a) the customer wants them or b) to make a softer string bed, and a vibration dampener is already being used.