In the case of the UK, out of 2.2 million men who were wounded in the war, 182 000 either died of their wounds or were left invalids.
Considering that the continental armies, i.e. France, Germany, Austria-Hungary, Russia and Italy had higher casualty rates than the BEF, I'd imagine that the sight of limbers invalids would be somewhat uncommon, although they may have been a more familiar sight in large population centers, like cities such as Berlin and Paris.