It's like changing the oil in your vehicle. Either time or mileage will determine frequency. Same for strings/cables. Even if they look good after several years and not a lot of use, I will still change them. I've not shot Compound regularly in about 10 years... but when I did I had a general rule... on my go-to bow that I about regulary practiced and hunted with, I generally needed to replace string/cable every year... brush busting in the backcountry chewed them up pretty quick. It only takes blowing up a limb once due to a snapped string to make the butt pucker a bit in this regard. For my back up bow that rarely left the case expect for an annual tune, I still replaced string/cable set every 3 years just as good practice. So yes, it's worth the money to have the piece of mind that your equipment will perform as is was intended to when it's time to kill something.
