The Naval War College Global War Games touched on this in 1988. Over the course of 1985-87 they gamed out a World War Three scenario till D+64 or so, but the 1988 Game was different. In 1988 the refs moved the time period ahead till D+75 and then created three possible scenarios' Stalemate, Red Dominant and Blue Dominant. From there the participants examined various likely outcomes. One of these included what a prolonged, non-nuclear, War would be like. From what I remember the general consensus was that it would take at least until D+135 for Blue to shift vital industries to a war time footing, beyond an increase of 15% or so from slack.
Here's a link to the relevant PDF.
https://www.usnwc.edu/Publications/N...ts/20-pdf.aspx
Benjamin