acharis was saying the press(and fans) would consider research a key-element in 4X-games, thus it might be a bad idea to sell it as a 4X.
(i think you should probably sell it as die-hard-4X or 4X meets total war or something)
a few questions:
will there be any (special) resources in your game ?
why do you want to game to (seem to) last shorter ("only" a few years)
i ll keep the rest of my comments to myself, because they all come down to "but you could research this, but you could research that" xD