What Nepenthes are people successfully growing ( ie pitchering) as a houseplant, not in a terrarium? For how long? Please try to estimate your humidity and light conditions.
I have found N. Coccinea to do well and am still struggling with N. Truncata and N. Khasianna. My humidity ranges from 50% in the day at 80F to about 60% at night at 76F. They are in a SE window but only get direct sun for a couple of hours.
Terrariums are fun but incorporating the plants into your environment seems like a better way to grow and enjoy them.