First off, one possible reason for the "keep bulb cool & dry" advice is
if the weather in their native habitat is cool and dry (i.e. the swamps
evaporate) during their natural dormant period. I don't claim to be
much of an expert on this, but winter in India/Thailand/SE Asia is
rather on the wet side, isn't it?
I had an experience with the plant that may be of interest. I have a
55gal tank with no CO2 injection, but everything else compliant with
the Dupla method: plenty of light, dupla fertilization, laterite in the
substrate, no UGF, etc.
Nothing grows well in this tank - must be something about Austin water
that just has to have CO2. Anyway, before I figured out all my attempts
at growing stuff without CO2 were entirely doomed, I put in several
(I think 3) crispus plants. These guys, like most of the other plants in
the tank, just slowly died off. I totally forgot about them and didn't
remove their bulbs.
Then I got the idea that the reason the [other] plants weren't doing well
was that the Ph was too high, so I bought some acid buffering solution and
tried that. The plants did somewhat better, but not enough to justify
continued use of the buffer (I feared for my fish). But the interesting
bit was that after many many months of dormancy, the reduced Ph triggered
the crispus plants to come back - they quickly grew leaves of about three
inches before settling back into the normal pattern of this tank: dying
Anyway, I guess the lesson learned is that under some conditions, it may
be possible to leave the bulb in the tank. I have no idea what's special
about my tank that allowed all three to survive, but they did.