I cant comment on its long term endurance but I can say this.
If its the 2k "Extreme" DTM Primer/Surfacer/Sealer ****, that stuff sands absoutley terrible. I find it to be very soft, and clogs up the paper very quickly. If you happen to catch and edge, or are not careful you will gouge into your just sanded finish. To me, its fine for small parts. But I would not want to sand an entire car coated in the stuff....way to much paper and time.