Your strings have already dropped tension before the first game

Polyester loses a significant part of its tension within hours of stringing, which is why professionals restring frames that look brand new.

A stringer pulls a frame at fifty two pounds. By the time the player walks on court, that string bed is not at fifty two pounds. Polyester begins relaxing the moment the tension is applied, sheds a meaningful chunk of it in the first day sitting in the bag, and continues to drop during play as the material is deformed on every impact and does not fully recover its shape.

This is the property that separates poly from every string that came before it. Natural gut and multifilament nylon hold tension comparatively well and lose their playability gradually as they fray. Poly holds its shape and its structure for a long time, so it looks perfectly healthy, while the thing that makes it play well has already gone. A poly string bed that has not broken can be completely dead. Most club players are playing on exactly that, because a string that has not snapped does not feel like it needs replacing.

Which explains behaviour that otherwise looks like superstition. Professionals restring several frames a day, change rackets at ball changes rather than when something breaks, and complain about a frame that has done nothing more than sit in the sun for an hour. They are not being precious. They are chasing a moving target, because the frame they started the set with is not the frame they are holding now.

The practical consequence for the rest of us is that stringing tension is a much less exact instrument than the number on the job ticket implies. Asking for a two pound change is asking for a difference smaller than the drift that will happen before you play. If you want a real change in how a frame plays, change the string, the gauge, or the pattern. Those effects persist. The tension number mostly does not.

I would add one heretical suggestion. If you play twice a week and do not break strings, a full poly bed is the wrong choice regardless of what the professionals use. A hybrid with a softer cross, or simply a decent multifilament, will hold its properties across weeks rather than days and will treat your elbow better.

Poly is a consumable that pretends to be durable. That is a strange thing to sell to people who restring twice a year.