The German terms stundenlang, monatelang, tagelang, wochenlang, and jahrelang are used to express durations of time in a descriptive manner. 

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Stundenlang translates to "for hours" or even "for hours on end," indicating an extended period spent on an activity and often emphasizing the intensity or monotony of the experience. This word can either be used as an adverb or as an adjective, in which case it needs to be altered to reflect the noun that follows. 

Stundenlang ritt er umher, um den Weg nach Hause zu finden.

For hours, he rode around searching for the way home.

Caption 19, Märchen - Sagenhaft: Hans mein Igel

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Und ich hätte wirklich stundenlang dir zuhören können.

And I really could have listened to you for hours.

Caption 42, The Voice of Germany: Isabel Nolte singt „Als ich fortging“

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Zurzeit muss man entweder eine stundenlange Zugfahrt in Kauf nehmen oder man fliegt.

Currently, you either have to put up with an hours-long train ride, or you fly.

Captions 22-23, DW-Nachrichten: Der Traum vom Hyperloop

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The word tagelang highlights a continuous action or state over several days, and is also often used in narratives to depict persistence or exhaustion.

Tagelang fuhren sie bergauf, bergab über die holprigen Straßen.

For days, they rode uphill, downhill over the bumpy roads.

Caption 44, Märchen - Sagenhaft: König Drosselbart

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Ich könnte tagelang von dir erzählen.

I could talk about you for days.

Caption 16, Xavier Naidoo Ich kenne nichts (das so schön ist wie du)

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The word wochenlang is also used as an adverb of time or an adjective that describes something that lasts weeks.

Das "Face" ist wochenlang beobachtet und perfekt gecheckt worden.

The face has been studied and checked perfectly for weeks.

Caption 15, Wintersport: Engadin Snow 2009

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Man kann auch von Menschen, die wochenlang unterwegs waren, die Deutschland als ihr Ziel ausgeben, etwas Geduld erwarten.

You can also expect, from people who were traveling for weeks, who identify Germany as their goal, some patience.

Captions 10-11, rheinmaintv: De Maizière führt Gespräch über potenzielle Sicherheitsgefahr

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In these last two examples, you can see monatelang used as an adverb and jahrelang used as an adjective:

Du kannst ja jetzt auch nicht monatelang im Prinzip ständig am Limit trainieren, du brauchst auch wieder eine Regeneration und so.

You also can't—for months on end now—be pushing yourself to the limit when training, simply as a matter of principle. You also need a period of regeneration, and so on.

Captions 52-54, Angelique Kerber: Ihre tennisfreie Zeit

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Da ist Technik dabei und die jahrelange Erfahrung und Tricks.

Technical [assistance] is there and the long years of experience and tricks of the trade.

Caption 55, Selbst versucht: Gepäckabfertigung bei Fraport

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Further Learning
You can find more examples of these words used in context on Yabla German. Also, try writing your own sentences.

There are basically two types of unpleasant realities that everyone has to accept at some points in life: involuntary and voluntary.

The involuntary realities are things that have happened outside of your control, whose necessity is undeniable—anything from your car needing to be repaired to having to undergo a medical procedure for the sake of your health.

The voluntary realities are when you actively choose to accept something you don't like because the advantages outweigh the disadvantages. For example, you take a new job because it pays well, even though you don't like the boss.

German has an idiomatic phrase for having to accept something that can fit either of the above realities: etwas in Kauf nehmen.

Das ist es nicht wert, dass wir dafür so viele Verschlechterungen dann in Kauf nehmen müssen.

That's not worth having to accept so many changes for the worse.

Caption 9, Deutsche-Welle-Nachrichten: Massenprotest gegen TTIP

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DWDS defines etwas in Kauf nehmen in both senses:

1. Having to put up with something (a difficulty or the like); having to put up with something unpleasant or uncomfortable by necessity.

2. Someone voluntarily accepts something negative (a disadvantage or unpleasant side effect) if the positive incentive outweighs the negative overall.

Zurzeit muss man entweder eine stundenlange Zugfahrt in Kauf nehmen oder man fliegt.

Currently, you either have to put up with an hours-long train ride, or you fly.

Captions 22-23, DW-Nachrichten: Der Traum vom Hyperloop

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... dass die einem normalen Risiko, wie man's zum Beispiel auch beim Straßenverkehr in Kauf nimmt, entsprechen.

... so that they correspond to a normal risk, as one would also have to accept in road traffic, for example.

Captions 50-51, Abenteuer und Sport: Fallschirmspringen

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According to Redensarten, the idiom originated historically with etwas mit in den Kauf nehmen. A buyer would sometimes get some additional goods with the purchase if the trader did not have enough small change on hand to give back to the buyer.

Also, lenders sometimes charged interest by asking borrowers for goods that the lenders didn't really need, but which they accepted in order to do business at all. This led to the meaning "to accept an unwelcome addition to something that is otherwise advantageous."

Further Learning
Watch the full-length videos above on Yabla German to see the phrase used in different contexts. You can additionally write some some sentences with "We had to accept that..." or "I had to accept that..." and practice translating them into German using in Kauf nehmen.