I think it is like a math problem. Light + humidity + soil + bugs + room to grow = healthy nep if you got three out of five right, at least. Light and humidity have to be two.
Whatever plant you have will grow best in an environment similar to what it is found in. If you do your homework, or have other people on this website do your homework
, you should be able to find out exactly what conditions your plant needs to thrive and make big pitchers.
For example, where I live we've been in a freak wet and mild period (even for Florida) for a while. It's been like a rainforest, really. But, between the rains, we get sunshine. I've got 10" N x Mixta pitchers, 6" ventrata pitchers, 3" amp pitchers, 5" coccinea pitchers, and so on. It's just good lowland conditions, room to grow, and all the free bugs we get living here.
The weather is bound to change, but for now I'm taking advantage of it.
I think if you submerge a pitcher it will rot. Just guessing.