A minimum of a two-year interval is required before continuing to the 30th degree, again with the intervening degrees awarded by name only.

But the amount of sand lost so far suggests that "a one- to two-year interval will be more realistic," he said.

More recently, the government has been considering a two-year interval.

Another complete set of surveys will be carried out in 1994 and at two-year intervals from then on.

A series of books was to follow at roughly two-year intervals.

A rough corollary is that you will get double the computational power for the same price at two-year intervals.

The girls had been born at two-year intervals.

Soon tournaments were held at about two-year intervals.

Since 1999, at two-year intervals, the same promises have been made and broken time and again.

Each committee is subject to renewal at two-year intervals unless the committee charter states otherwise.