Upload & Sell: Off
This is one of those things where there is no right or wrong answer.....there's only a right or wrong answer FOR YOU. If 30 minutes works for you, great. If 3 hours works for you, that's great too. The key thing is in finding what works for you and what doesn't.
I'll even take it a step further and say that learning to read facial expressions/body language/mannerisms will pay off big time. I feel like if I spend 5 minutes with a couple I can tell right away if the meeting is going to be a long one or a quickie. Some people just want to meet quickly, just to confirm you're the person they want to book. That could take 15-20 minutes. Some people are really social and really like to talk. For them it could take an hour or more. The quicker you are at figuring out what type of couple you're meeting with, the easier it is to tailor your meeting to their personality types. Spending too much time with a couple that doesn't want it or not enough time with a couple that does can work against you.
For me personally, I know if someone sits and talks with me for more than 45 minutes, there's a very high probability of me booking them. That being said, if I pick up cues that tell me the couple doesn't want to sit there for an hour, I'll shift gears and get it to the point a lot quicker than I normally would.