Mine are currently in a mix as well but I might experiment and move some to the sphagnum moss. Do you think it would be harmful to move them into new pots at this time of the year? The older plants need new soil and the new ones are in pots that are so small I am afraid they might not be able to cope with the cold this winter.
Mine are in a peat/sand mix also but i have a few ive just chucked in moss until i get around to repotting them all and they seem to be doing fine. I dont like moss as it over grows the plant unless you keep pulling some out. I repot mine in spring/summer and its never hurt any. I just thought dormant/leave alone, growing can mess with. hehe! So your ment to repot them in winter? When the pitchers die down?