[2022] How long can I stay offline before the server wipes off my land/house ?

That depends on the rules and / or laws of each specific server and can change at any time. You could check server rules and the law screen to see what's there. On official servers unclaiming generally may not happen before a player is considered abandoned by the game, happening after 5 days of inactivity. If stuff is actually unclaimed after that time and when is up to the player government.