Digging in, a TOAW III "improvement" ?

[Currahee]

Yes, they can accumulate supply while on D, if they don't actually fire. The problem is with longer-range artillery, there's almost always going to be some battle within range, maybe not an important one, and that will drag down supply, and therefore, readiness. It's worse if you have a unit with different ranged guns; even if only a few of the longest-ranged guns fire, it still drags down the supply for the whole unit; really, designers shouldn't put different ranged guns in the same units, but some do, especially in the older scenarios.