How do I make a timed walk speed script?

I am trying to make the players walk speed go down to 10 after 70 seconds has passed. I have a very simple code that changes the players walk speed when the join the game. I just assumed if I put a wait(70) before the code it would wait 70 seconds then activate, but it doesn't.

game.Players.PlayerAdded:connect(function(player)
	player.CharacterAdded:connect(function(character)
		character.Humanoid.WalkSpeed = 10
	end)
end)