What would you do when you …?

Do you often hear expressions such as

• "What would you do when you go to college?"
  
• "What would you do when you work?"
  
• "What would you do when you have a boy/girlfriend?"
  
• "What would you do when you serve in the military?"
  
• "What would you do when you are married?"

? Many people use this kind of expression to persuade another to change some current habits. Why do I have to make daily decisions now based on some future scenario? If my options are fewer in the future, I will adapt then. Why can't I utilize the larger number of options that I have now? This reminds me of someone I knew when I lived in a dorm. He doesn't want to clean up the room because "rich people hire housekeepers to do the clean up". The problem was he did not have any housekeeper at the time. If you persuade me with reasons such as health, hygiene, knowledge, frugality, or any the good morals, I'm willing to listen. But "What would you do when you …?" is not a convincing argument.