I got six 'cute stuff' seedlings back in the spring. 3 went in the ground (which aren't doing too well), 2 went in 3-gallon containers (on the left in this pic) and 1 went into a 4.75-gallon container. The latter is huge. The plant and its peppers are almost as big as the California Wonder beside them. The Calwonder is on the right.
I have to confess, though, I use Miracle Gro.
There were no organic fertilizers at my little hardware store and I don't have a car.
I was trying to get a picture of the big pepper on the plant, and then I said "to heck with it" and cut it off to get a better picture.
The banana is for scale.
Who knows, maybe it would have gotten bigger!
But to answer the OP's question, I'm pretty sure they reach full size before they start ripening. And that can take forever. That's been my experience, anyway. I can see why red peppers are sometimes 3 times the price of green ones at the grocery store.