I brought this topic up specifically with shapeshifting, but more generally, is the Concentration maneuver per spell or in general? If it's per spell, then it seems that maintaining a spell is far more taxing in Genesys than in any other system I have read, particularly since there's no minimum duration beyond the end of your next turn. Actually, either way it's a huge potential Strain drain if the caster needs to make any other maneuver.
One suggestion I read was make a spell that can be maintained last a minimum of 1 round per rank in the casting skill or in knowledge. Or simply make spells encounter length.