there's no point in staying any longer; it's time to leave
A set phrase used to indicate that one should not overstay one's welcome or that prolonging a visit is pointless. Often used when someone has already stayed too long or when the situation clearly calls for leaving.
It's late and there's no point in staying any longer. Let's head home soon.
Since there's no point in prolonging the visit, I'll take my leave as soon as my business is done.
Compound of 長居 (nagai, 'long stay') and 無用 (muyō, 'useless, unnecessary'). The exact historical derivation is uncertain, but the phrase is conventionally understood as 'a long stay is unnecessary'.