When the very first flowers start to wilt, you should cut the spike as
close to the base as you can. This is GOOD for the plant as it then
commences vegetative growth.
The spike containing all the perfect flowers should be treated as any
cut flower (talk to a florist if you have any questions) and they will
last as long -- or longer -- in a beautiful vase than on the plant
itself. I am a commercial grower from florida.