It might be helpful to have a strong base in one (so, training as a hobbyist, 10 years is reasonable), but it doesn't take that level of exposure to be able to make use of what's in other arts you train in.My advise to anyone who wants to combine styles is to do each style for a minimum of 10 years and apply it. It's not complicated. It will happen naturally. Now to create a new style that you want to teach to others,, well now that's an entirely different question.