His mechanics now take each plane apart once a year for heavy maintenance.

FORBES: Lord Of The Warbirds

This involves getting shots of tiny amounts of the allergen in escalating doses, usually once a week, until you reach the maintenance phase, when you'll need one shot every month.

CNN: Finding relief as spring allergies rage on

And once these sales are made, the customer becomes low maintenance and recurring.

FORBES: Magazine Article

He argues that the Federal Aviation Administration does not oversee the maintenance of aircraft nearly as closely as it once did.

WSJ: Book Review: Attention All Passengers

Once in operation, the machines run continuously, stopping only for maintenance and the occasional breakdown.

ECONOMIST: Why paper making is becoming less volatile

Drilling under Plan A will stop this weekend once the drill bit reaches 1, 247 feet (380 meters), then the drill will receive scheduled maintenance before resuming early next week, engineer Rene Aguilar said.

CNN: STORY HIGHLIGHTS