The thing you also have to keep in mind about dubia size. They have their nymphs live, and then it takes a couple months for them to get to adult size, so a thriving colony will have all different sizes of nymphs, smallest being <1/2 cm. If you keep a set amount of adult females and feed off the nymphs as they get to the size you want them, you can feed any size reptile, from small geckos up to adult beardies.
I like keeping a larger colony now as I have found that ALL my reptiles LOVE and fight over freshly molted roaches. Every day when I go look, I'll have 2-3 that have just molted. Even when one of my reptiles goes on a hunger strike, they will go after them. (The first time they might be wary, but after that they come after them.)
My panther will not eat out of my hand, but will come running to me if he sees a white roach in my hand...
I love my roach colony.
It has saved me loads of money and is especially handy in the winter when other insects maybe hard to procure.
Matthew