You don't have to put them in a terrarium and Neos are quite humidity tolerant. Lighting is still important and in the wild, have exposure to longer winter light hours than in the summer. I keep mine either just below, or right at Catt growing lighting requirements and lessen water in the winter. I too have Neos still in spike and flower. Just keep watering them as usual, and when they're done flowering, reduce the water for winter.