Hi there Krone,
Before I start I have to tell you that I´m a complete novice in bonsai. I´ve just started reading both books about bonsai, pruning and tree biology.
My wife who´s a "certified" gardener says that even if it could be ok to collect yamadori now since the buds are swelling, the risk is that it could be a cold snap (I meen it´s still february) making the newly gathered yamadori die.