Active Durability vs. Static Durability
"Durability" is one of the main factors in choosing the strings for all tennis players. "Durability" is measured by the number of ball impacts until breaking the string. This is "Active Durability", which is easy to recognize if you are standing on the court at least a few times a week. All the string manufacturers aim to develop more 'active-durable' strings.
Even if we all love playing tennis, we sometimes have to leave the tennis rackets behind for a while for various reasons, such as personal schedules, weather, travel, or you may have a few spare rackets etc. What will be happening to the unused strung tennis strings? We tested and got the data for the "Static Durability."
Static Durability Test Data
Japan Racket Industrial Association measured the elasticity change of the unused tennis strings on the rackets.
All the tested tennis strings (Polyester/Monofilament, Nylon/Multifilament, and Nylon/Monofilament) start stiff after two weeks. Nylon/Monofilament is most 'static durable' but becomes 110% stiffer after three months.
The loss of elasticity can not only reduce the performance of the strings but can also hurt players' wrists and elbows.
What we learned
Ideally, the tennis strings should be replaced after two weeks, but this is unrealistic for most of us. So, Japan Racket Industrial Association recommends replacing the tennis strings within three months.