I believe that a couple things happen:
1) If the soil is too wet, that will breed mold. You just want to keep it damp, but not like you would during its growing season.
2) If you have had a mold problem during the growing season, it would be a safe thing to apply something during its dormant period.
Remember that dark, cold, wet conditions breed mold just like hot and humid do.
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Like someone pointed out, it depends on how you value your plants. And how many that you have.
Cleary3336 and Banrot are 2 things that we sell, and they are what we use on a regular basis for all plants. ( cp's and non ). We use them as preventive measure and in the event of something coming up.
If you have a few plants, a little will go a long way.
But like some people have said, they haven't had a problem, while others just won't take a chance. It just depends where you want to stand.
I would do whatever I could to help keep something from killing my plants. I have some VFT's that are many years old ( they are my baby's ), as well as some Sarracenia. I would die if I lost them!!