This is what I recommend too. If someone declines me politely with a reason like "Sorry I'm busy today, maybe next time." I'll probably wait a week or so and in

This is what I recommend too. If someone declines me politely with a reason like "Sorry I'm busy today, maybe next time." I'll probably wait a week or so and invite them again if I want to eat lunch with them. If they reply with something shorter like "I got something to do, sorry," with a less kind intonation I probably wouldn't invite them again.