Buy more pull ups?

DS has been daytime pee trained for about 4 months and just two weeks ago finally started pooping on the potty. Prior to that he would wear underwear all day but when he had to poop, he would ask for a diaper. We would put it on him, he would poop, then we would put underwear back on. Two weeks ago we forced the issue by requiring him to sit on the potty when asking for a diaper for an increasing amount of time (setting a timer) and then letting him have a diaper for only 5 minutes, and then letting him sit on the potty for as long as he needed/wanted to poop. After a couple of days of that routine he started pooping in the potty with no turning back.

So now we just have to deal with night time, which he still wakes up most mornings with a wet pull up. We are down to 2 pull ups but still have about 30 diapers. I am debating using up the diapers for night time vs buying more pull ups. I have a younger daughter that will eventually use the diapers so the economics of it aren't a big deal but I would rather use what we have available now. He previously associated the diaper with "no pee" when he was mostly pee trained but not quite ready for underwear all the time. So that could carry over to the night time. Or, he could revert to pooping in the diapers.

What would you do? Buy more pull ups or use the diapers for night time.