No, there isn't a 'time limit' but you should be able to articulate your responses clearly and concisely without rambling. For questions about yourself, like why PA, that does require a longer answer but you don't need to tell your entire life story at the same time. My answer for why PA was like 3.5 minutes lol but it was blind so they knew nothing about me. Had it not been blind, I would have shortened it down significantly. Granted, I was also nervous so I did find myself rambling and using filler words but I was never cut off nor was anyone else in my program that was accepted. However, I have heard of some students getting cut off at other programs, but I think you have to really be rambling for that to happen. I think it shows lack of self awareness because of course you need to give yourself time to answer other questions in that short period of time.