ok thanks for all te replies, especially those last 2. i charged the fiends in and maxed so 3 fiends vs 5 elves. i kill enough to take one fiend out of combat, so with only 2 in b2b i can reform like that? cuz i got this other guy telling me that by reforming, i'm losing support attacks and thus pulling models out of combat.
it didn't matter for that game as the spears rolled insane courage and so the fiends got obliterated by the silver helm bus with his prince and BSB. it is good to know though.