My ventricosa grew at what I thought was a fast rate, til I got other neps.
I have a Spectibilis, Vent, and a Spec x Vent, and the Vent is the slowest of the three. The Spec x Vent is the fastest.
It's not really the most exciting plant in my collection either... but it has a very fond following and is probably one of the most popular plants to grow, Ventrata is the other one.
If you get the growing conditions right, which is pretty much any decent amount of sunlight, you can do a Vent.
In a year my plant probably doubled in size from your size actually, but I have it growing under very strong artificial lighting and a very loose, coarse media, which to my estimation promotes healthy root expansion.
My motto is, if you're waiting for one Nep to grow, buy 5 more to pass the time!
These plants don't hit dormancy so the growing season is really up to you. My plants grow and pitcher over the winter here in California too, and some of them pitcher even more and with more color due to the cooler tempuratures which some of them like more than others.
Welcome to TerraForums and happy growin!