Gander,
Nightbloomers will get really big really quick. You do need to pull it up and thin it out though if you want a lot of flowers.
Nightbloomers are especially good at reproducing. Sometimes you can wash the soil from one and have hundreds of babies.
I pulled a few up last night that overwintered in dixie cups a la Sean.
I had 2 maturing plants and 6 more starters in that one dixie cup although it had already jumped the root system out of the cup.
Tim