Strengths are hard to answer without sounding completely cocky. Weaknesses are even harder when you're asked the same question 3 times. I wasn't sure if I wanted to answer the same way (keep in mind, I had almost a week in between the first interview date and the second), or do I want to say something else. The problem with that is that you don't want to diclose too many "weaknesses" because it basically makes you look weak and flawed. You want your strengths to outshine your weaknesses, so KISS. Keep it simple, stupid.