I was curious for those that know their water's mineral content how often they descale. My total hardness out of the tap is 8ppm, which is very low.

Of course, there will be outliers from the people who make one espresso every other day and the people whose veins run brown.

And I figure the information here might be a useful thread for all espresso enthusiasts.

There's an excellent but very detailed resource for this called Jim Schulman's Insanely Long Water FAQ
that you can use to calculate the scaling rate for a given hardness, alkalinity, machine use rate. It's currently available here:
http://www.big-rick.com/coffee/waterfaq.html

The above site may not be its permanent home. Check this Jim Schulman's Insanely Long Water FAQ topic for current info and location for that FAQ.

If that 8ppm total hardness is not a typo, you are off the chart, not sure you'll need to descale ever.

Thanks for the FAQ!

And it's not a typo, the hardness here really is 8ppm. Of course, we have really high alkalinity (~360ppm) and sodium (200ppm) levels, so cutting with some distilled water to reduce pH and sodium, and adding a dozen or two ppm's worth of CaCO3 helps out to balance the lack of any hardness (going off of http://www.scaa.org/PDF/ST%20-%20WATER%...V2009A.pdf). Calcium and magnesium are nearly nonexistent.

Off topic, it's completely useless for brewing beer. I get ultra-purified water from my lab and add the salts corresponding to the style of beer I'm brewing.

At only 8ppm, you may need to descale the machine in another 5 years, if that. That is very soft water. My water is 135ppm and I descale about once a year as PM but could go longer than that.

I also enjoy really soft water and haven't needed to descale in years (although I always check annually). I don't believe in rigid descale schedules, unless of coarse you know, based on your water, how often a descale is required.