Around 15 months with mine and still love it.
I have used an old 10 channel Yamaha mixer and an A&H Zed14 prior and the SiX is noticeably better sounding to me. More transparent and open sounding, better pres and eqs with better headroom. It has been some years but I used the Zed14 a lot and think it sounds fantastic. The eqs sound solid and it stays clean when pushed. It’s huge compared to the Six though, and the monitoring isn’t nearly as flexible.
I compared Ableton’s glue compressor with the same settings as the g-bus comp on Six and the SiX comp sounds much better to me. I haven’t messed with a ton of other software compressors, but I run all my mixes through the Six g-bus comp and the difference is noticeable to me.
I wanted a clean mixer I wouldn’t mind having my instruments pass through before going into my Babyface Pro interface, and the SiX is perfect for me. It’s clean as can be until you start pushing the comps and eqs, then imparts a hint of warmth. I don’t see myself needing another mixer ever again.