It is a long road that has no turning

Proverbial Meaning: Nothing lasts forever, even the most boring task will be over eventually.

Literal Origins: Sometimes a journey can seem very tedious if it is along and follows a straight road, but even the longest road in the world must come to an end and have a turn.

Common Usage: This proverb would perhaps have been thought by some people  employed in a long, boring task but isn't all that well-known in modern English.

See also: Even the weariest river winds somewhere safe to sea