Why should he persist now in so fruitless a task?

Tracking suspected medical dumpers was an often fruitless task.

This isn't a completely fruitless task: much recent research suggests that will power is, in some ways, like a muscle and can be made stronger.

To attempt to foresee the many varied business ideas that future entrepreneurs will devise would be a fruitless task.

Trying to prove that is almost a fruitless task.

He wasted no more than a second or two in that fruitless task.

Too often the men withdraw, while the women find themselves exhausted by the fruitless task of trying to reconcile permanently hostile elements within the family.

So-why must I be driven back to a fruitless task?

It was a fruitless task, but a vital one to help shed light on the work.

I would rather try to roll up the stone, however fruitless the task, than sit idly looking at it, and doing nothing!