Saying you have to 'keep printing money' to cover debts is meaningless. All money is printed (or keystroked) into existence. Governments impose a tax burden payable only in the state's currency (so that people are forced to offer their output for sale in that currency), then they provide that currency.
The way to be fiscally responsible with your currency is to print enough so that everyone has a job, but so much that you're overrunning your output capacity and increasing inflation. Keep interest rates on bonds (if you choose to issue them) lower than your GDP growth (and since you're the monopoly issuer of your currency, you have control over interest rates) and you won't have issues with expanding debt % [1].
The first response to this is usually "well, Greece" or "well, Zimbabwe". The crucial difference in those countries was that what they owed was not their own currency, but foreign currencies.
[1] http://www.cfeps.org/pubs/wp-pdf/WP53-Fullwiler.pdf