long-continued

It dissolves readily in cold water, and is converted into sugar by long continued boiling with acids.

The previously dominant animals did not submit without a severe and long-continued contest.

Long-continued lactation—that is, beyond the physiological limit of about nine months—is especially a frequent cause.

Sharp hammering at the door, long continued, finally brought an end to Barrington's nightmare hours and Seth's deep slumbers.

After using all his strength in long-continued efforts, he succeeded in loosening the bar of his bedroom window.