Megan is upset because she is apparently older than 26, and among people who marry, half do so below The intuitive conclusion is that the number of potential partners is decreasing as time goes on. The Half Plus Seven Rule is an unwritten rule that asserts that it is creepy to date anyone who is younger than half your age plus 7 years. As the graph shows, there is a lower limit and an upper limit.
Cory Doctorow - Wikipedia
Enjoying "long walks on the beach" is a romantic activity stereotypically associated with dating; specifically, it is commonly listed as an interest in dating advertisements and, more recently, online dating profiles. It is likely that many people who list this in their profiles have never, in fact, taken a walk on a beach or may not live near enough to a beach for it to be a viable suggestion for a date. In this comic, Randall lists "long walks on the beach" as an interest on a dating profile. However, while a romantic walk might last for half an hour or an hour before, presumably, moving on towards another activity, Randall suggests he likes walks that last several hours or even overnight, suggesting potential mates bring a tent to camp out in. The title text suggests that those who say they like long walks on the beach are being disingenuous, or not forthcoming. He just wants someone who wants what he does; to walk an indefinite, indeterminate distance well beyond the comfort and expectations of everyone else. I rewrote the explanation and title text.