Unwearying

Mr. Collins repeated his apologies in quitting the room, and was assured with unwearying civility that they were perfectly needless.

Source: wiktionary

As a child that has fallen happily asleep in its nurse's arms, and wakes to find itself alone and laid in a strange place, and searches corners and cupboards, and runs from room to room, despair growing silently in its heart, even so Portly searched the island and searched, dogged and unwearying, till at last the black moment came for giving it up, and sitting down and crying bitterly.

Source: wiktionary

Night and day are given over to pleasure And they think it will last a thousand autumns, Unwearying autumns.

Source: wiktionary