I'm a little perplexed by the "maximum of three roundtrips". I'm guessing that it's the first three roundtrips that qualify once you register (starting the later of June 15 or 30 days before you register). In other words, if you fly LAX-SFO three times in June, then LAX-JFK three times in July, it looks like you get double miles on the short flights... right?

In that case, you may want to do some careful planning re: your registration date if you want to maximize the promotion. Tricky.