Large Object Shadows Shorter Distance Than Small Object Shadows

I’ve been noticing recently that the larger objects in my projects are having their shadows fade out long before the smaller objects, as can be seen in the attached pictures. It seems extremely counter-intuitive to me and it means that in my project, I have to massively increase the shadow distance if I want to have decent-looking results.

The first picture is taken at the threshold at which the large desk’s shadow disappears, whilst the second is taken from around 3-4x that distance - as you can (with difficulty) see, the shadow on the watercooler to the left of the desk, and rest assured that the shadows for the plants and other coolers are also still being rendered.