"I long ago realized that I could reach far more people by writing something, than by walking down the street with a banner."
- John Brunner

John W. Campbell used it in The Derelicts of Ganymede:

"...Get your stuff together and pile it in Lifeboat Seven, that'll be whole, and it's the biggest...

Duke Stetson pulled the releasing lever. Automatic doors opened, and a powerful spring gear drove the little twenty-foot ship clear of the gleaming monster.

Eando Binder used this phrase in Murder on the Asteroid in 1933:

In the wall nearest the hull was an air seal. He opened this. In the tiny chamber revealed rested a small ellipsoid metal object with a bulge of steel-glass on its top surface — the “life boat.”

Due to the constant dangers of meteors in space which might at any moment crash through an ether boat, each space vehicle carried one or more of the life boats. They were simply little one-man ether boats, miniature models of the larger craft, equipped with small but efficient rocket motors. If for any reason the larger boat became unmanageable, damaged, or useless as a vehicle, the passenger could then embark in the life boat and propel himself within reach of rescue. Each life boat was equipped with a radio. They also carried food, oxygen, and heating apparatus.

Hanson, holding the little man in his arms, smirked as he saw the dull metal ellipsoid boat, for it entered his plans of the moment. On its side was emblazoned the same number as was on the outside hull of the bigger boat — P-322-M-505...

Stooping, the fat man grasped the life boat by two of its many rocket tubes, raised it to his chest, and pushed it away from him forcefully. He knew that the gravitation of the asteroid was so small that it would fail to draw back again the little craft as it shot away from him like a blunt bullet.

('Murder on the Asteroid' by Eando Binder)

But before the little object passed out of view altogether, a ghastly white face with wide, fearful eyes appeared in the glass bulge and looked back to Hanson with a pitiful expression of horrible despair,

Hanson began to laugh then, and laughed insanely till he once again took off the suit in the ether boat.

“Mine, all mine!” he shouted, waving an arm to include all the visible topography. "He didn’t deserve any of it, the little rat—and now it's all mine!”

Doc Smith used this phrase just a year later in Triplanetary:

Through the airlock, down through several levels of passenger's quarters they hurried, and into a lifeboat.