[quote=@Nilesapa]
Like others have said, it's the most interesting of the bunch if only because I get to march in formation with big red shields and shout in Latin.  
[/quote]

Well, no, not really. The Empire survives, but society and technology still changes. 

EDIT: To elaborate - Roman military strategy would change to meet the standards of whatever era it survives in. And with former barbarians (and conquered peoples) assimilated into the Empire, you'd be looking at a very multicultural, and multilingual empire that only distantly identifies as Roman.