WOW!! I could never in my wildest imagination thought there was so much to learn about one plant! Thank you so much for the information about my big boy! I'm saving this post too.You can use pretty much any potting mix that work well for you and your plants. Whatever you use, you just have to adjust watering.
I prefre bark (orchiata) based mix rather than having moss as a base mix.
Maudiae type hybrids can last very long in bloom. Most commonly they last two months easily. Three is not uncommon and four months is definitely possible. Masterisanum lasts very long in bloom and many of these hybrids have mastersianum in its linage somewhere.
Mastersianum is also known for a very long spike. Things like lawrenceanum can have pretty long spike as well.