I repotted several 1+ yr S. leucophyllas in mid summer and, a few weeks later, unpotted them to send them to someone. *During that short time, they had an enormous amount of root growth. *But I use a mix of LFS and volcanic rock (the large, irregular perlite stuff), a combination I think encourages better root development.
Sarracenias don't really go dormant, so I prefer disturbing them when in full growth. *That way they have an active metabolism to heal injuries and fight infections. *Maybe they're dormant in a refrigerator, but mine are clearly active in the winter, even with air temperatures sometimes below 0F and and a pile of oak leaves overhead. *They aren't doing much, but they're doing something.
Peat breaks down when aerobic and most roots need aerobic conditions. For that reason, muck farmers need to balance the drainage needed for crops against the increased decomposition of their soil resulting from the aerobic conditions. *Decomposing peat in a pot can lose its nice structure and become an amorphous goo that restricts the passage of water and air. *That isn't good for Sarrs.