The phrase 'at three-year intervals' is correct and can be used in written English.
You can use it when discussing how often something happens, such as a recurrence or a cycle. For example, "The vaccine needs to be administered at three-year intervals."
The percentages are regularly adjusted at three-year intervals based on changes in the economy.
A director could recuse himself from decisions with potential conflicts, he said, and a different fund representative could approach the United States during the next appeal for donations, which typically occur at three-year intervals.
The first film in the series was released under the title Star Wars on May 25, 1977, by 20th Century Fox, and became a worldwide pop culture phenomenon followed by two sequels, released at three-year intervals.
They interviewed subjects about their diet and administered tests of thinking, learning and memory at the beginning of the study and then twice more at three-year intervals.
New generations of semiconductor technology typically advance at three-year intervals, and today the industry can see no further than three and possibly four generations into the future.
The researchers tested the subjects' mental acuity at three-year intervals, and tracked their degree of adherence to the Mediterranean diet on a 55-point scale.
These restrictions will expire at ten-year intervals.
Most of the women (81%) completed at least three assessments at two-year intervals.
The World Convention of Churches of Christ since 1930 has sponsored mass meetings for fellowship and inspiration at five-year intervals.
Between 1995 and 2001, memory was measured in 16,010 subjects over the age of 70 years, at two-year intervals.
Getting a mammogram at two-year intervals lowers the harms while still reaping the benefits of the test, Dr. Keating explains.
