10 hours (i.e. enough for a complete loop of all FFT sizes in blend) is enough for me.
Still having a fair bit of trouble around the 480k/20k test area (around 4-5 hours into blend), with either hangs or rounding errors. I'm testing at 489x9/1.37v with memory at 1223 on 2.50a divider. It seems to like 1.28vtt the most, any lower and the board gets stuck at POST after a reboot, any higher, and blend fails sooner. MCH is at 1.54v and Tread is 8. Vdimm is set to 2.220v, although both do just as well with less. Have tried various voltages skews & ref changes, but still can't get through a complete error-free loop at this speed. CPU temps dont go beyond 65°C so I'm starting to suspect the board, but if anyone can offer any hints I'm all ears!