I use house rules that chop off the last of the four Xs. Military momentum games are neither historically plausible nor fun(after the xth time). It just boils it down to the most efficient rush. Who did that? Khan? How long did that last? Momentum play excludes so much of the game, is made challenging only by adding handicaps (deity, etcetera), and you just quickly reach the point where you are just trying to push a won game with no really interesting decisions looming.
I play something like:
Casus Belli: No war declaration unless a just cause exists, as defined by:
A. If attacked by AI civ.
B. If AI diplomatically attached to attacking AI.
C. If AI detonates first use nuclear weapon.
D. If valid imminent victory by AI.
E. If barbarian.
F. Raids xxxxx
G. Fleet interventions xxxxxx
Vengeance: All wrongs must be put right.
War Gains:
A. Limited to three distinct periods of war.
B. Limited to capture of 0-3 AI cities per period of hostility.
C. Limited to capture of no more than 6 AI cities per Casus Belli.
Those are not all of my rules, I have them jotted down on various scraps of paper. This is just the basic stuff.
So, if you start on a land mass in a multi-continent game and none of your neighbor AI wants to attack you, what do you do? I play with aggressive AI and raging barbs for the action, however, even getting a war from neighbors I can only take 6 cities. Playing huge, marathon, multi-continent maps 6 cities isn't a lot given that you can't just wipe out the AI. So, you have to deal with their culture (I play flip back too). So, it gets complicated, you really don't always know how a game will unfold or how you can win.
One thing you realize with self-limiting rules like these is just how often we simply bulldoze through real world type issues by just declaring war and burning cities to the ground (which not allowed to raze in my version). I enjoy playing the game for enjoyments sake, not just for score or comparison with others. Some of the most fun games playing like this are lost games in which I played well but events just conspired.