And that's where I come to the second must-do on making mating work. I think the writer needs to make it obvious that these people would choose to be together even without the mating instinct. The instinct may be what makes them completely unable to walk away from the person they see (at first) as being the least-acceptable partner for them, or the worst possible choice they could make, but it can't be the only common ground they have to stand on by the end of the story. In other words, the romance has to be believable even if you didn't have the mating instinct going on in your book.
However, I do think that having that mating instinct is just an extension of most people's desire for a "soul mate." That one person (or people) that was fashioned just for you. That perfect match. With shape-shifters and destined mates, it's a more culturally recognized institution for that kind of species, but that doesn't mean the people involved don't have as much (or more) work cut out for them in making the relationship work. Plus, for me, the mating thing? Is hot. I love the instantaneous connection (and, in my books, that means sexual connection with a heat-rating that's off the charts and orgasms that register on the Richter scale), but insta-connection should never, ever equal insta-relationship. Everyone has to grow and earn their happy ending, mates or no mates.
Why I Love the Marriage of Convenience Plot.
Intricacies of the Marriage of Convenience Plot.
Where's the Sexual Line in Paranormal Romance?
Types of Paranormal Romance.