In two thousand two the group had suggested such screening tests every one to two years for women forty and older.

VOA: special.2009.11.18

The United States Library of Congress appoints an official poet, called the Poet Laureate, every one to two years.

VOA: special.2010.04.05

The new guidelines say women age twenty-one to twenty-nine only need to get a Pap test every two years instead of yearly.

VOA: special.2009.11.25

Most of us are locked into contracts that only make it money-smart to buy a new one every two years.

ENGADGET: This is the Modem World: You Use THAT?

The RNIB says that children under 16 and adults over 60 should have an annual eye test and the rest of the population should have one every two years unless they have been advised otherwise.

BBC: Photo of an eye examination

If you're at high risk of certain eye diseases, such as glaucoma, get an eye exam every two to four years up to age 40, then every one to three years between 40 and 54, and finally every one to two years at age 55 and older.

CNN: Nearsightedness