I have used blooming Phals in bathrooms, no window, and in other parts of the house where light was poor. Problem with Phals, you need to know if the spike is still gowing and forming new buds. Lack of light would cause those buds to die off if the buds were still small.

Phals are used alot in house decoration and staging. They are put in places which don't contain good light.

My opinion is that the flowers will last in either circumstance as long as the plant is not over-watered and is basically healthy.

I wouldn't leave the plant in no light for more than a few weeks, maybe a month as the leaves need light to survive.

One other point, I have had Phals in bright light and the flowers lasted for 6 months. As long as strong sun is not hitting the flowers and the room is very hot. Phal flowers last almost forever as long as the plant is healthy.

Jane