For me, it's generally great to have lots of interesting content that's written from the heart and unique, and not-so-great to have boring stuff - one more round of "What's your relationship with Imoen?", "Tell me of Gorion and Sarevok", "We must find Irenicus!" and the obligatory "So, Child of Bhaal, huh?" Edwin's romance, for example, is unique - it deals with Edwin's personality and crisis of conscience(he was supposed to kill CHARNAME for the Red Wizards and didn't); Sarevok's romance is also very Sarevok'y, concentrating on his, um, manly stature(gulps).
Romance conflicts are good, and four-five lovetalks would be fine until the first one, but keep in mind that you can write a mod conflict with Anomen, but writing a conflict with Edwin, Haer'Dalis, Adrian, Kivan, Kelsey, Solaufein, Darian and Waukeen knows who else? And then updating it each time a new mod springs forward? A hopeless effort, I say.
I would say it's best to have eighteen or twenty or more lovetalks before confession and the variable becoming 2, because the romance _before_ the love confession is the most interesting part, the "will-they-or-won't-they" part. Besides, multiromancing is popular before commitment, so that the player has room to breathe and choose and maybe pretend she's not flirting with That Guy at all.
After commitment, I'd still have a minimum of five-eight lovetalks, because otherwise it might feel like the NPC's finally gotten CHARNAME into his bed and then fallen silent, because he needs nothing else from her. Which is a major turn-off.
For ToB, I'd say nine or twelve lovetalks with a short(40 min) timer is fine, if you already have a SoA romance. More is better, less than eight would probably feel too sparse.
Mind you, that's just me, the girl who wrote twenty extra player-initiated conversations for one(!) of Xan's romance paths in ToB alone just because she felt like it.