I think the window only really closes for Ancient Era and early Classical Era civics. Since this is the "struggling up from barbarism" phase, I don't want the civics to be too good at that point; otherwise, there isn't much reason to change.
Even Classical Era civics are still good for a while. Monarchy is supposed to be the best "big empire" government; how it compares to Federation is something to test. Public Works is the best Welfare civic for building production until Superhuman; Mercenaries is the Military civic that produces the most units at the top of the XP curve until Volunteer Army.
I'm trying for specialization in the later civics, like MAD and Shadow War. That way I think it's easy enough to comprehend the civic and decide if it fits your current civilization. It also frees up room for other civics to possibly move into the vacated area. Example: As long as Intolerant gives +2 XP to units, I don't want to give XP to any other civic category outside Military and Religion to avoid breaking the curves. If I take away the XP from Intolerant (keeping the unit production bonus -- think "crusading hordes" rather than "holy warriors") and give it to Theocracy, then Rule civics, like Junta, can get into the XP area and not worry about breaking anything. This is where I see Naval Supremacy as fitting in.
Even Classical Era civics are still good for a while. Monarchy is supposed to be the best "big empire" government; how it compares to Federation is something to test. Public Works is the best Welfare civic for building production until Superhuman; Mercenaries is the Military civic that produces the most units at the top of the XP curve until Volunteer Army.
I'm trying for specialization in the later civics, like MAD and Shadow War. That way I think it's easy enough to comprehend the civic and decide if it fits your current civilization. It also frees up room for other civics to possibly move into the vacated area. Example: As long as Intolerant gives +2 XP to units, I don't want to give XP to any other civic category outside Military and Religion to avoid breaking the curves. If I take away the XP from Intolerant (keeping the unit production bonus -- think "crusading hordes" rather than "holy warriors") and give it to Theocracy, then Rule civics, like Junta, can get into the XP area and not worry about breaking anything. This is where I see Naval Supremacy as fitting in.