High boost and ethanol are hard on plugs.
This stuff works great, and IS functional, but it does tend to quickly coat the plugs with brown tinged, yellow/orange deposits on both of the electrodes and insulator, so his tuner suggested he change them out every 4K-7K miles, or every oil change.
Some radical, or 'edgy' tunes for maxxed out hybrids, or BT kits, also tend to wear down the center electrode very quickly as well.
For a basically factory stock turbo, 'bolt-on' modded FiST, with just a flash, or even a 'safe' custom tune, the plugs should last at the very least 25K-30K miles, even with hard, or 'short trip' use.