Ya, you definitely write more idiomatically but I think that to a certain degree you also write better parts because you know which notes are louder because of how much air/bow is needed and many small details like this. With all of these points already being made, my reason for posting is that I think you're time plots are way off. In my opinion, to build up enough knowledge of the instrument it should really take less than a month of LIGHT practicing. The point of learning all of these instruments as a composers is knowing many small orchestration details and these can be found in less than a month. I personally feel VERY strongly about this topic and have actually put it to work myself, I've play guitar, bass, banjo, cello, viola, violin, trumpet, trombone, saxophone, flute, clarinet, piano, percussion and organ. Once you learn an instrument of a family, which this will take a couple weeks of regular practicing it is MUCH easier to learn enough about the others, I learned what I feel is adequate for composition on violin and viola in less than 5 hours.