You are way more impressive to a client/customer if you are considerate of their time. Basically, I don't believe that my time is more important than your time, but I want my time to be considered.
Now, lets talk about how a sense of urgency can help your sales. For my business, there is a lot of customer communication. It usually starts with a customer requesting prices for printing and design. If I were to sit on those requests, another print shop would ultimately get the jobs. What I do, is make the pricing very high priority. That way, when they receive my price and they haven't yet received prices from my competitor, that gives me time to sell it. Usually, my customers make a decision about buying at the time of the quote. So why would I sit on those prices and wreck my chances? I don't, I use my sense of urgency to get it to them right away. And I do the same with general inquiries.
My business is not that different from other businesses as far as selling and they are the same rules across the board. When a customer is shopping for services, they are ready to buy. If you sit on the inquiry, someone like me is going to pick them up as a customer.
When inquiries come in, you need to look at those as potentially new lifelong clients and get them the info they request quickly.