A. I’m glad you’ve been lucky so far. But it’s unlikely you’ll match every designer’s gauge in every yarn. And if you’re even a quarter stitch off over 4 inches, you may wind up with a poorly fitting sweater you don’t like to wear. If you’re substituting yarns, another important question is “do I like the fabric?” You may have hit the suggested gauge, but is your fabric loose, limp and likely to loose its shape? Is it tight and stiff? Consider both aspects before you decide how to proceed. But definitely, swatch, swatch and reswatch until you’re happy. I know you want to dive in, but a little time now may save days of work.