PCF2131FT OTP refresh

[LiaoYF]

Hello. We would like to know the OTP refresh mentioned in datasheet. 

"It is recommended to process an OTP refresh once after the power is up and the oscillator is
operating stable. The OTP refresh takes less than 100 ms to complete. "

For end product, is this required each time the product power on or only needed once the first time our product power on?

What's the intention of this OTP refresh? to better maintain the content stored in EPROM?

[guoweisun]

For a watch it is essential that the timing calibration can be made after the watch is fully
assembled. In this situation, the supply pads are often the only terminals which are still
accessible.

[LiaoYF]

It seems the answer didn't answer the question regarding OTP refresh process.