the den and catt can be cut back when they're dried up, as wendy says.
they won't rebloom off the existing spikes/stems. the phal can be
cut back about a third of the way down the spike after the flowers
fall off, and it *may* rebloom for you. if it does, it's stressful
for the plant. personally i don't cut my phal spikes until they
shrivel up. i'm more interested in longevity of the plant overall.

--j_a