How Long Should House Guests Stay?
A weekend is the understood unit. Beyond that, you are being accommodated rather than entertained.

The short answer is: when they've been invited to. Everything else is nuance.
A weekend is the understood unit of a house guest. Arrive Friday evening, leave Sunday morning, and you remain a welcome guest. Beyond that, you begin to edge toward a visitor who is being accommodated rather than entertained.
The traditional rule was three nights. The modern reality is closer to two. People are busier, houses are smaller, and the pleasure of company fades quickly into the burden of logistics once a guest overstays the rhythm of the household.
What matters most is not the number but the courtesy of clarity. Ask, when you arrive, what the hosts' week looks like. Offer to leave a day early if they seem tired. A good guest is attuned to the signals — a host who starts mentioning Monday's meetings is offering you an exit.
Leave the room as you found it, strip the bed if that's the household's way, and leave behind a note and something small — flowers, a bottle, a book you've finished. The gesture is the point.
Good guests are invited back. Great guests are the ones who know exactly when to go.
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