Thus, it is recommended that the sheath be cleaned once or twice a year.

Sorry, he was told, the engineers' contract stipulates that the windows are cleaned once a year.

Gold does not smudge, so it only has to be cleaned with soap and water once in a while.

There was this enormous cast-iron oven, see, and it got cleaned once a year, I think.

"We've already cut custodians; classrooms only get cleaned once every third day," he said.

They were only cleaned once a week, remember.

Some experts feel the drive heads should be cleaned once a week, others believe twice a year suffices.

During air-conditioner season, filters should be cleaned once a month.

Some of the rounds, once cleaned of mud and oil, were perfect.

If there are windows, they are cleaned once every 12 years (I asked).