As you've said your minimizing use, but if you do have to drive it, I'd recommend getting clips of the cold start idle, warm idle after at least 10 mins of driving and probably cold and warm driving in cab if you can hear it from in there. If you have access to a video/slr camera with mic, do it with that and set gain/attenuation/volume manually and record from the same distance, it may be overkill for most, but it keeps it apple to apples. Your phone may even have pro video settings.
In all honesty the clip provided doesn't sound much different to mine without the Nulon "special sauce" added and it's sounded like that for the last 150k km's with little worsening. Been worrying for nothing for years! If you want to be horrified by engine sounds to make yourself feel a bit better, look up Ron's piston slap thread on here. 8 f**king cylinders of pure stress for the poor guy. Don't sweat it just yet.