I buy a game, and unless I get the DLC(s)/Expanions pack(s), that’s all I’ll ever have to pay. Civilization V: Over 2000 hours. Pathfinder: Kingmaker/Wrath of the righteous: Over 1000 hours each. Stellaris [0]: Almost 1000 hours.
[0]: Some people hate the Paradox DLC style, personally I think it’s amazing. Content DLCs are accompanied by free feature patches, cosmetic/minor DLCs are well, minor. No one forces you to get all of them. And thanks to this DLC policy, Stellaris will soon turn 6 years old while still getting regular updates.