I fitted a set of Spidan springs to my TDI in early 2012 and proceeded to do approximately 100,000 miles with them over the ~8 years that followed.
Audi's own springs are really prone to torsion fractures and, frankly, not worth their price, especially when you consider how much better the car rides on Spidan springs. Audi springs also don't compensate for the inevitable lift that's introduced by the use of Koni FSD/SA dampers, which was the original reason Spidan springs became so popular. Spidan springs are made by GKN, who are a quality OE supplier.
One of my front Spidan springs finally broke about 9 months ago. Considering the tough life they've had on Lake District roads plus countless other journeys through rough mountainous areas, I can't complain. I immediately ordered some identical replacements, but one of them broke within weeks. Annoyingly, I was in Belgium at the time, but managed to find an online supplier and a garage who were happy to let me use their ramps. I replaced the spring and have done 6000 miles since then, including some very rough gravel tracks in the Alps. All seems well.
One possible conclusion is that GKN produced a poor batch, hence the rash of early failures over a short time period.
Cheers,
Tom