It is assumed that longer messages take longer to compose. But that's only true if you're starting from scratch every time. You should instead write one good generic message and send it out to many people, only inserting one sentence to reflect on something specific to the particular profile.
The reaction you'll get is, "He's really slick at promoting himself." Most women will speak this sentence with a curled lip and a tone of disdain, but if you're looking for women who like a guy with an elevator pitch, this just might work.