I have a call center that handles all the calls and emails from people requesting more information before they buy my program. Every now and then, someone will call repeatedly, or demand to speak to me personally before buying. I don't call these people back, and I've instructed my office not to either.
Why? One thing I learned in sales is that those types of people usually turn into problem customers who aren't worth selling in the first place. I track all data very carefully, and although I get very few returns, one thing I've noticed is that 100% of returns have come from people who asked endless questions before buying. Plus, why would I spend time on a low-margin sale like that? When a retailer calls, interested in buying a few thousand copies for resale, that's another story. I stop whatever I'm doing and take the call. Why? Because it's high-margin. I can justify spending my valuable time with that person. But I cannot spend time on a skeptic who wants to be "sold" when the profit from that sale might pay for my lunch, if that.
Don't waste time on high-maintenance prospects. While you're busy catering to their every request and demand, the good prospects are buying from your competition.