How do you know that a record is really worn?

When you are playing side one and you start hearing the tracks from side two.

OK, then lets assume you bought a new LP and its sound quality is absolutely good with no play noise/pops or whatever. And your turntable is set up perfectly and you take care of the vinyl.

When do you normally start hearing those play noise and pops? (Maybe after 50 play?) When do you start hearing the sound gets muddy? (Maybe after 200 play?)
After how many times of play?

I have many LPs that look very clean with no scratches but have lots of play noise and pops. Also, I have many LPs with lots of visible scratches but sound very good with marginal play noise and pops. So, visual inspection alone would not be enough to tell one LP's condition. Also, some of the new LPs I bought have annoying play noise and pops right at the first play.

Hello Jan, it sounds like you have a lot of later pressings where they tend to sound pale, thin, and lose "prescence". Early pressings can have more "pop".

Depends to some extent on the vinyl used. I remember Supraphon and Hungaraton LPs that started showing audible wear (clicks, pops) after a very few plays, while other labels stayed silent. Unfortunately the more rigorous (aka, anal) I became in my record cleaning, the better the result. "Unfortunately," because it takes at least twice as long as it used to take. Dave

On a serious note, if you use a well adusted TT, clean your records well and maintain the system you should be able to get several hundred plays out of a vinyl record before any significant loss of signal. Clean and a properly set up TT is the key.