Every game ever created, whether solitaire or a 16-player epic, has some sense of scope. In fact, I would argue it's the most important facet to consider as a game designer - in effect, it's a simple question:
"Who are you?"
Are you a five-star general, plotting grand strategy across Europe? Are you a solitary soldier running across the battlefield, trying not to get killed for God and glory? Are you a futuristic Marine squad commander, trying to lead your troops through an alien-infested derelict? Are you the supreme commander of a civilization, or a single-cell organism? It doesn't matter - IF the scope of the game matches correctly with the answer to that all-important question.
I thought about scope very heavily when designing Star Requiem: Humanity's Last Stand. Since my last game was so (overly) detailed, I was initially a little hesitant about making the game 'epic'. But as I really started to work on the backstory, I realized what the game was truly about. Originally the game was going to be a war between two roughly equal sides- the Order and the Lost. The Lost were a group of humans who split off from the main new colony of New Terra to practice their own form of religious expression (read: evil) and eventually, seeked to reclaim their soulless brethren in all-out civil/factional war.
Now, this was interesting, but it had two problems from my point of view: first, religion is always a touchy subject in any game and balancing the factions might prove tricky since I planned to have a heavy demonic influence on the units/systems that the Chaos used. But the second, and far more important reason, is that the scope just didn't feel right. The stakes didn't feel high enough. You're fighting a war against.... yourself, essentially, and if you lose... well... you'll be going to a different church in the future. While important, it didn't feel epic... until I came up with the Xyl.
Here, we have a force that is (until now) unstoppable, unnegotiable, and uncaring about eradicating humanity from the face of the universe. They're not looking for reconciliation, or even slaves. They want everything dead. Except for them. Period.
Now that's a threat! And in that context - where humanity must essentially 'learn to fight' again and essentially become what had nearly destroyed it (irony!) the scope of an epic game and feel made sense. Technologies would have to be uncovered; ships and fleets would have to be created; systems would have to be scouted and reconned, and offensives planned; and events would happen that would effect entire systems. Most importantly, the enemy threat could build slowly enough for the humans to have a chance, but without quite knowing when the Xyl will start actively destroying and conquering systems, there is a tension that stretches out well, even across game-years (each turn represents 3 months).
So, in the end, after much internal pontification, I decided that SR will most likely be a pretty long game to play. Somewhere around 12+ hours for a full game. And I worried about that. I know that will turn off a lot of people who are now used to Euro solitaire games that take 30-45 minutes. And there is nothing wrong with those games - you need some bite-sized diversions now and again - it can't all be Silent War if you hope to have time to enjoy the breadth and scope of gaming! But the stakes are what they are; and I just didn't feel in the end once I had nailed down the backstory and the enemy that the story - and the conflict - could be told in just an hour or two. Since SR is meant to tell the story of an epic struggle between two galactic empires who are waging a war of desperate annihilation, the plot deserves its time to grow and mature. And so it shall.