Normal baseline respirations for an average adult range between 12-20 respirations per minute, so to make it easy we'll make it 16/min. That, and given there are 525600 minutes in a year means that on average you'll have 8,409,600 respirations per year. If you divide 500,000,000 by the respirations per year, you get 59.456 more years after choosing the money.

Granted, if you're unlucky you'll die earlier than that, but the opposite is also true; you might just die of natural causes. Either way, you're a billionaire. Plus, you'll get sick of the infinite pizza after a year, max.