Most people I know ignore the VC wins and play until concession. Under these conditions, unconditional surrender conditions you might call them ;) The most important factor after Center collapse (e.g. Russia Falling) is the overall Naval parity between Axis vs Allies, and the status of the IJN especially. It sounds like in this case, if Tokyo is under threat, then the USN has them totally beat.
If Germany holds the Center and threatens London, but USA holds Tokyo and can concentrate its full attention on the Asian mainland/European, then the potential for a deep endgame is pretty strong. Especially if the Western Allies can begin liberating Soviet land for themselves. This is why some people regard the VC win as hallow, and prefer “Concession” to the Technical Knock Out, as the best way for satisfying game resolution.
I think its best to figure this out beforehand and just ask your opponent how they prefer to resolve the game. If the opponent is willing, and you think you still have a chance, then I would play on!
Often the VC win kills the play, at precisely the moment when things start to get really interesting. For example, I know a lot of Germany players who would get a lot of enjoyment out of playing a few more rounds and spending all that extra loot they pilfered from the Russians. Likewise, I know quite a few Allied players, who would relish the chance to lay the smack down on Tokyo, especially to avenge the fall of Moscow in the other theater. So in that case, the 8 VC auto-win, just like 6 VC auto-win, can end up being on auto-buzzkill.
I mean, some games you just need to play out until someone throws in the towel, or you’d never really know who had the upper hand ;)