@Private:
Not sure whether anyone else has said it, but holding Moscow is often not necessary, if the allies still hold Egypt.
As G will usually have odds on Moscow at some point, then saving that Russian stack by abandoning Moscow and withdrawing south to the Middle East can mean that losing Moscow does not lose the game.
The experienced contributors to this thread will know all this, but thought it should be stated for any less experienced players.
At some point defending Moscow is just protecting 3 IPC (unless if you hold Irak and the African territories) and the troops and the Allied planes sitting there can be tied up at pretty minimal cost for Germany (stack of troops strong enough to hold near Moscow which is is being reinforced with cheap units, + planes + fast movers sitting elsewhere).
Russia holding Bryansk for as long as possible is important. After that, not losing Russia while keeping pressure on Stalingrad and Caucasus seems to be the strategy. Many of the German players build lots of mechs and later add some tanks that can head south and really cause big problems. Ideally Russia is able to keep this mass busy long enough (e.g., trading territories and chipping away at it, or forcing that force to stay north) for the UK to get their act together.
UK fighters are particularly valuable because they can shift from protecting the Russian front to protecting the Middle East and they also add to the strike value of the Middle East stack.