他们已经理论了很久了。

Tāmen yǐjīng lǐlùn le hěn jiǔ le.

They’ve been arguing for a long time.

理论课一般都很闷。

Lǐlùn kè yìbān dōu hěn mēn.

Theory classes are usually pretty dull.

你们还在为这个无聊的事情理论啊！

Nǐmen hái zài wèi zhège wúliáo de shìqing lǐlùn a!

You’re still arguing over this boring thing?!