Duration of table tennis balls

hello,
what is the duration of average table tennis balls to be usable?
i noticed that there is some sort of powder covering most of table tennis balls that can't be removed by rubbing it with the hands, however, this powder ensure great amount of spin on the ball, i have some used balls without the powder ( they are somehow glossy in comparison to new balls) and it take too much force to do any type of spin on the ball.

Thank you in advance.

Hi Hassan,

The balls are best when they are new but without the powder on them.

You can wash them before using them.

The balls do wear slightly with more hitting but there is not a huge difference that you need to worry much about.

You can use a ball till it has a crack in it which can be many hours of play.  Some of the newer plastic balls have tended to break easily but they are getting better.