Most forms and seeds have this covered, but there is a handful that don't have a bending time listed.
also, I repost my suggested armour penalties here:
this rule, among others, also requires certain seeds to verify the extent of the somatic component. the lightning seed is pretty specific, but I don't see much info on the movements required for other seeds. Perhaps the complexity of motion could be inherent in a certain DC level, and the armour penalty could incur a maximum DC limit, and benders wearing certain armour simply couldn't exceed that limit, even when overbending?