It's normal for them to stretch a little when new, but it should only be needed a couple of times. After that it should just need adjusted as the clutch wears.
Check the ends of the cables for fraying where they connect to the barrels, that's where they break.
And be sure to keep enough free play in the adjustment. As the engine torques it pulls on the cable, so if you don't have enough slack it constantly has the cable under tension. I adjust mine so it has 2 or 3 quarters worth of free play at the lever gap. Basically, turn the adjuster out so there is no gap, pull the lever and insert two stacked quarters in the gap, then turn the adjuster in until the quarters just fall out.
I've gone through a few cables and all but one started to get play in it long after my last needed adjustment. In my experience it is a sign of the cable starting to let go (break). Check both end closely and look for frayed wires.
i keep mine even looser. I keep it as loose as possible that will allow me to get it in to neutral. if you go to loose, that will cause problems. It doesn't matter how loose as long as it doesn't tighten up under wide open throttle. Here is mine below. I have run this setup for 37k miles. 22k on stock cables and 15k on a gen 3 barnett with no issues.