The I guess it's all on how much experience you have. However from my experience, not having too much is a good thing, because if you have a lot of experience they will ask you really difficult questions. I have 25 hours only but I did a huge amount of self study, so even though they asked me basic questions, I was able to elaborate in-depth. I think the best amount if experience is just enough to demonstrate your commitment and passion, but not too much to the point of having crazy questions thrown at you.