I've been re-reading the infamous guide to playing hard-to-get, The Rules, and their modern update, Not Your Mother's Rules.
While I take these guides with a grain of salt, the authors do explain very simply and easily what I've been saying for years: a) men value the things they have to work for and b) men will put as little possible effort into relationships to get what they want, so if you let him 'have' you easily and quickly, he'll never go beyond the bare minimum.
One thing the modern Rules advise girls is not to respond to texts, emails, or online messages from 6pm Friday night to 6pm Sunday night. While I usually consider Saturday my "dead zone" for boy communication, I'm going to try extending this.
Not that the boys are knocking down my door....