When one daily drives and have a feel for the car, one knows fairly quickly when something seems to wear. Especially when you need to turn the adjuster every couple of months to bring the shock back in range.
Upon removal I noticed one of the shocks is worn enough that I can pull it out by hand relatively easy.

The QA1 shocks on the rear axle were installed in the same year as the fronts, but I've only had to 'up' them one or two clicks over time.

The design of the QA1 shock, and also the Viking dual adjustables seem quite a bit beefier than the thin Hotchkis/Fox shock.