I think that as a doubler it’s easy to consider your ability level “good enough” on a secondary instrument. Check your doubles below, and ask yourself what you can do to raise the level of your playing. I’ve given just a few examples of “next level” techniques on each instrument.
Can I play up to the highest notes (4th octave C, C-sharp, and D, for example) with delicacy?
Can I play the lowest notes with power and confidence?
Can I double and triple tongue fluently and without having to think about it?
Has my tone progressed past the “duck” phase? Is it rich, dark, and flexible? Even in the high register?
Am I thoroughly comfortable with the various F fingerings—right, left, and forked—and prepared to choose the right ones even while sightreading? How about E-flat fingerings?