I bought this 6 months ago. When planted the bare bulb was about 18" tall. The new plant is now 50" tall. It is planted in a 10" clay pot in Reifers Magic medium.
I need advice on whether I should leave it alone or add more medium.
Since it's inside due to the frost warnings, I took new pics.
I don't think you need to add any more medium to the pot. It looks pretty happy with what you've got it in. They do bloom alongside the immature new growths (at least mine does), so if it starts to come out of its dormancy in the spring and produce a new growth, you might see a spike. I would suggest that you let it go dry between waterings at this time of year. Mine usually (though not always) drops most of its leaves during the winter, at which time I treat it like one of the deciduous Mexican lycastes (lots of light and long stretches of dryness between minimal waterings). When it's dormant, andersonii can also handle much lower temperatures than it prefers while it's in growth (although, like you, I too would bring it indoors if there was a frost warning, even if it was dormant at the time). Good luck with your plant. I think you'll be impressed when it flowers for you.