A balloon can only expand so far before it bursts as its composition is finite. It's an interesting thought however, that some claim the universe can seemingly expand forever. If so spacetime has a beginning but no apparent end therefore it might or might not say something about the infinite. It's hard to imagine that in the very distant future after protons and quarks have decayed whether anything will be left to define the passing of time as we now understand it. According to quantum theory any form of matter left including strings would be unable to completely stop vibrating so the universe will never reach a temperature of absolute zero. But then again what about leakage of energy due to quantum effects? If the vacuum is caused by quantum fluctuations would these define the passing of time alone or would vibrating strings that still survive define the passing of time even if they were dispersed by cosmic distances?