This is an interesting story. If sex were all I was interested in from women, then this seems to be as good a strategy as any. It's logical, based on small concrete achievable steps, etc. It breaks down a social process to it's utterly simplest terms. Some may be offended by the idea that sex is the point of a relationship, but to a lot of people it is, either implicitly or explicitly. If it's among consenting adults that both know what they're getting into, who are we to judge.
Seven years age difference is nothing. Where I live, a lot of women won't date a man 1 year younger than they are but think nothing of marrying a guy 10 or more years older. This was a royal PITA when I was trying to date in college because I was mostly interested in women who were past the parties and drinking phase when I actually had a chance to be interesting to them.
These things are subject to cultural differences and we shouldn't be so quick to judge. One of my childhood friends (younger than me), married a guy in his 40s. Her family and everyone were very supportive and thought there was nothing at all wrong with this. This seems illogical to me based on the relative lifespans of men vs. women, but as I've often had to learn the hard way, cultural norms are often illogical. Yes, I do live in the American south and Yes, things are somewhat different here. It's not necessarily better or worse, just different.
I don't think what the OP is doing is creepy or even necessarily wrong, as long as he's honest and up front. Not everyone wants a happily ever after romance. Some people are more interested in passion and excitement, and when those dry up, they move on. To each his own I say.