A time to renew a tatami

There is a method of "a reversing", "changing tatami facing", and "new tatami" to exchange a tatami mat.

When you sit down on a tatami or lie, there can be the thing that clothes are accompanied by a threadbare small rush from tatami facing.
That is a sign for reversing a tatami.
It is also a sign of flip, when tatami facing discolors, and to become brown.
Generally an aim is 2 or 3 years.

A rush grass becomes fluffy from tatami faxing, and when a stain occurs, it’s a good idea to change the tatami facing.
Fluffy means when rush grass wears out to become fluffy and is to stand.
It is a sign for changing tatami facing, which generally in 7 years.

If unevenness of tatami facing becomes remarkable and when you walk and feel it soft, let's replace it for a new tatami.
Generally an aim is 15-30 years.