From my understanding, setting leap seconds 20 years in advance is not a good id...

Deestan · on April 23, 2011

According to my calculations, the Japan earthquake will not require us to adjust a leap second - at least not within the next ~761 years.

The Japan earthquake shortened the day length by 1.8 microseconds. [1]

1.8 microseconds * 365.25 days * 20 years =~ 0.01 seconds off. Not enough to require an update, even less an urgent update before the 20 years.

1.8 microseconds * 365.25 days * 761 years =~ 0.50 seconds off.