Just finished up a game a couple days ago with some friends, and it always seems to come down to a valiant last stand at Moscow followed by either an admission of defeat or (as is the case with the game we played) Italy is contained and the Allies can still hold Egypt to some extent.
That is an interesting idea that could be considered when the Germans look as though they are a couple turns away from taking Moscow. I’m not sure I’d do it just because of the amount of time to move those infantry would make it totally obvious to the Axis what you were doing. At that point you are completely giving up Russia’s IPC income to the Axis which is not very wise. The advantage to this Alamo battle is that the Axis also lose a lot of units and Germany remains licking it’s proverbial wounds for a turn of the game at least.
So while it’s interesting and I have never considered it, I’m not sure it would be worth it.