If you invited a long term friend to your home for dinner next Tuesday and he said “I’ll let you know later” but didn’t say how much later, how long would you feel obligated to keep the invitation open? Until Monday night? Or Tuesday morning? Or not at all? My attitude is not at all. The moment a person can’t plan on coming, that’s the moment I can’t plan on cooking. I don’t cook dinner every night and mostly just do healthy snacking during the day. But he likes special cooked dishes that I prepare for him occasionally (when he can commit in advance to coming).