A lot of play-testers say it drops in tension and becomes unplayable. But what if you started at a higher tension and once it dropped it became perfect?? And how does it different for NG, Multi and Polys?
Most strings lose tension immediately after stringing and settle within the first day. For example Babolat RPM blast strung at 55 on a lockout machine is down to 50 once the strings are clamped, may drop another 6 pounds or so after the first day, so tension reading about 44. Then after the first time it is used, it may drop another 1-2 pounds. Each time after maybe a fraction of a pound until it plateaus.
When playtesters say it drops tension, they are likely referring to it just losing elasticity, resilience. That is a different thing that occurs after the string wears out.
Gut on the other hand does keep tension fairly well. Had gut in my racquet and after a initial loss of about 5 pounds from 60 down to 55, it was in the 50s for many hours...
Strings wear out, don't worry too much about it, find a tension that works and stick to it.
All strings (except perhaps prestretched Kevlar) lose tension after stringing. It will stabilize. Question is where does this tension stabilize. All strings will lose tension from ball impact. Again the question is where does this loss plateau, if it does at all. Some like NG or multi will plateau, others like extra thin poly don't. The TWU database is a guide. YMMV because of your playing characteristics.
If it matters a lot, you can get the racquettune application for ipad/phones, etc. As a stringer I use that application to check consistency of stringing, and measure daily decreases in the tension of my racquets. Surprisingly there is a pretty large window for playability. Before I purchased that application I used a stringmeter from tennis warehouse to check the stringbed tension.
I find that with thinner strings the tension will drop considerably regardless of how high you set the tension. However, I have found that sometimes strings can settle at a little higher tension if you string one frame tighter than the other. The initial loss is going to be the same though regardless of the reference tension.
In my experience. Softer polys loose tension faster than firm polys. It will depend on each string. Most of them loose tension gradually. Some of them keep tension very good and than drop significantly. This is my experience with RPM Blast. Very frustrating because you don't see it coming.
As for the level off. Yes off course it levels off at some point, otherwise they would fall off. But I imagine most people change the string before the tension levels off.
I think there is no point in thinking much about it. When you feel like they are too soft or when you see they move all over your racquet its time too change them.
Also, tension lose depends on your game. Hitting harder-faster tension lose.