I am also 5'9" and hold a 58" cue at the end. I have played full time with a 12" extension for several years and I'm quite happy with it. I find that I prefer the balance with a little bit of length and weight behind my grip location. A well-made extension is hollow with most of the weight being in the joint, so the weight difference between a shorter one and a longer one is negligible. Standard disclaimer: this is what works for me, YMMV.