Twin Snakes is damage buff that's very important for PGL/MNK, you will want to prioritize keeping it up. That said, keep in mind the duration, you will basically have Twin Snakes/True Strike rotation, Boot > Twin > Snap > Boot > True > Snap > Boot > Twin > Snap, etc. This won't change until you get to level 30 and unlock Demolish. Then you will alternate Twin/True and Demolish/Snap as durations allow.
That's a good catch, surprised no one else noticed it xD