I think most people in this thread are taking these names a little too literally. In game terms these are just gates to compensate for the fact that GalCiv's tech tree is a bunch of parallel branches instead of a web. They do not dictate player or AI behavior. The current names do a good job of describing typical behavior in the early, mid, and late game.

Age of Expansion - In the early game most players will be settling their near-by planets and building up the infra-structure of their planets

Age of War - Once everyone has settled their own areas they will find their civs butting up against one another. One very common, but not inevitable result of this is war in order to continue expanding your empire. Even if a player peruses a completely peaceful path it is very likely that the AI will be declaring war against each other and the player at this stage.

Age of Ascension - The end game. Victory conditions are within sight, and civs start bee-lining toward them.

Will there be games were no one declares war during the age of war? Of course there will be, does that make it a bad name? No, it simply describes a common response to the the situation that will usually be found  in that part of the game. I guess I don't understand the objection. If you are avoiding military conflict during a period named "the age of war" in the tech tree (and as far as I know, nowhere else), does that name somehow decrease your fun? Does it offend your sensibilities as a gamer? 

I like the name "age of war" personally. Conflict is probably more accurate, but lacks the gravitas of war, expansion, and ascension. Names like "age of strife," don't zero in hard enough on the fact that this is an era characterized by civs bumping into one another, strife can come in many forms and to me implies internal rather than external conflict.

The problem with naming a technological era as the 'Age of X,' where X has nothing to do with the technology, is that it assumes that X is what's going on during that time period. Calling a technological era the Age of War is problematic because it makes the assumption that it's a time of notably more warfare than in the other technological eras, as otherwise some other descriptor would have been chosen for the era. However, it is well within reason to expect that there is no real difference in the overall amount of warfare going on in the galaxy from mid-Expansion all the way to the end of the Age of Ascension. If the Age of War were called the Age of Hyper Fusion and Quantum-Fried Chicken, that issue wouldn't exist and there would be a real tie-in between the age name and the subject being divided up into time periods.

In my opinion, if you want to divide games up into named eras, it is better to make the names of the eras have some connection to whatever you're using as the divider between eras. In this case, however, we have a political activity (war) being used to describe technological progress, and this makes very little sense unless there really is a noticeably higher incidence of war in the time that you spend in the 'Age of War' portion of the technology tree. It makes sense to describe technological eras by key technologies or key thinkers within the era, not by political activities which aren't necessarily happening.

joeball, you make a convincing case in theory, but I'm at a loss as to how this would play in practice. There are no real benchmark techs in the GalCiv2 tree or what we have seen of the GalCiv3 tree. Also, the parallel trees mean there is no tech that everyone is guaranteed to research. One possibility may be that the age could be named after the first tech you research in an age or the last tech you researched in a previous age. This ends up making as little sense as the age of war because no one tech is going to make sense as defining an entire age.

The reality is that if the gating feels artificial and arbitrary, so will the era names. If there is a natural logic to the ages, I think fitting names will present themselves. Honestly, many people in this thread are making big, if reasonable, assumptions about the nature of the techs in the different ages. Maybe the vast majority of techs in the age of war will contribute to your military effectiveness. If this is so then the name isn't detached from the techs it is describing, but instead it is an accurate description of the techs acquired during this time frame if not of the actual political activity.

Also, it's just a name. If it bothers you, pretend it's something else. Every time you open up your tech tree and see "age of war," just say "age of sentient hot dogs" or whatever in your head.