It's good when you plan to leave for about 8-10 hours . Usually what happens in such a long span is that first raider attack will trigger 1/3 or 1/2 traps . The next will trigger more . By the third raid every raider knows that your traps are used up . This is when the raider Avalanche starts . Unless and until there is a full attack on your base which gives you a nice peace treaty , those raiders will clean your base over the night/during office hours .