Nothing can last. Empires rise, and empires fall. Human planning and random events will topple even the mightiest in time.
We should have a few more good centuries since we have had only one Civil War and have haven’t yet conquered our neighbors except culturally.
Of course, limiting the power of the dependent class will become even more critical. Caesar rode it to power becoming so powerful a threat to the status quo that its defenders killed him and unleased the wars resulting in the empire.
The institutionalization of the payoff to the lumpenproletariat ate away the vitals of the City morally and economically. Only by exploiting the rest of the world could the loot be raised while becoming a permanent interest for war and expansion.
In Rome probably a majority of the citizens were on the dole and the whole society was supported by slavery. We are not in that situation so there is a limit at which government can extract and redistribute. As far as federal taxes go the number oscillates around 19-20% over the last century.