You don't need to put your iPhone in airplane mode at night. Just set the Do Not Disturb, and be done with it. Allow your messages to come through with no disturbances. . . You can still call out if you want. Set a time for when it is inappropriate for people to disturb you and set that as when you won't be bothered.
I don't go to bed until the wee hours of the morning, but my iPhone Do Not Disturb is set for 9PM. The only people who can get me after that are close family and friends whom I've put in my VIP list or someone who dials my number twice in succession with a short period and they better have their tail end on fire.
I already use the Do Not Disturb Schedule function. It’s just that on Airplane mode, my iPhone doesn’t use up charge. I don’t keep it on a charger, setting it down in various places or putting it in my jacket while asleep. I don’t need to use it while sleeping, but don’t necessarily want to power it down. Close friends and family know to try mobile and land line to reach me.