no not usually, but there's no harm in doing so if you like when there is a new version of macrium reflect out.
the disc/flash drive is just a live os used only to restore the images you've created with the program on your pc usually.
the only time i can think of you will need to update your restore media is if there is a major change in macrium reflect and the type of images it creates so the live os can't then read and restore them or can't restore to a new type of partition table/file system.
eg. last time i think you definitely needed to create a new restore media was for use with images created of a system using the new gpt partitions and uefi secure boot.