Tan colour line from left to right is the trip from France to Moscow, 1mm line weight = 6000 soldiers, black colour line from right to left is the trip back to France. The line slowly thins and diverges like a tree branch until 422k soldiers are whittled down to 10k returning. Not quite the outcome Napoleon had intended.
Given the Russians burnt out everything they left behind, which is one big reason the line keeps thinning, I doubt they would have survived very long on the land they occupied. But I'm no Franco-Russian war historian, I just like data.
I think the idea is they would have caught up with the Russians and defeated them in battle, and could have taken supplies there. By marching back through the scorched earth they actually maximized their exposure to it.