It just depends on how temperate or tropical your conditions are. The native moss from Alaska will not grow very well in an indefinite Nepenthes enclosure, but sphagnum native to further south in the warmer subtropical* areas of the state may very well tolerate more tropical conditions for a very long time. Sphagnum is very hardy. Even the Alaskan moss grows in highland Nepenthes conditions, it just doesn't grow very well...
Too bad meadowview doesn't ship to WA! Dang it.
This is a good thread to start though, and a good question to ask for any carnivorous plant grower.