Cattleya: Flower Sheath and Dormancy.

[Manfred Busche]

Hello there.
A very good book states that, after a Cattleya plant
has produced one or more Flower Sheaths, the plant
goes dormant i.e. requires a 'Rest Period'.
That book sounds very clear to me - but amongst the people I know, there is nobody who cultivates his/her plants accordingly. However, many 'complain' about empty Flower Sheaths !!
My question is:
Dormancy after appearance of Flower Sheath required...
...(a) for all Cattleyas ?
...(b) not for all, but indeed for some?
...(c) not at all?
I hope that one or the other of the knowledgeable Cattleya Aficionados out there will share what they know; thanks very much in advance.
MANFRED.