I bought this rhombicaulis last December from YG Park, Cameron Highlands. The plant is grown in the high humidity tank amongst my heliamphoras. The room temperature range are 25°C - 31°C. The humidity are kept are 85% to supersaturated. Three 2ft florescent tubes light the 2 ft tank.
When I got it it has two pitchers (dimpled and other cut off), since then I have 7 new pitchers. The large pitcher is as big as the came with the plant.
I also bought two pots of cephalotus from Cameron Highlands. One was kept near my bedroom window and the other amongst my highland nepenthes plants. Night temperature in my bedroom averages 17-18°C.
The one that kept near the window died after two months and the one that grow amongst the Highlanders almost went that way. It had only one pitcher and one big leaf left. So I moved it into the high humidity tank. And voila the plant is regenerating with new leaves.
I can only conclude that humidity is more crucial than temperature drop. And that you can grow heliamphoras and highland nepethes in high humidity.
Choong