Some authors take this a good long way into specific theological territory, with marriage for time and all eternity and, once you convert, you have to leave all your old friends and family behind and furthermore you can't tell them any of the details of your new life because they wouldn't understand and/or it would endanger someone. But across the board, there tend to be some obnoxious themes like the Fated Love. I mean, it's one thing for there to be The One. Vampire (and related) fantasies often take this to a whole new level by having unrelated third parties have visions about your One-ed-ness, and complex political shenanigans being enacted to either thwart your One-ed-ness or take advantage of it or whatever.
Some of these series also have the No-Divorce-Commitment. It's a stripped-down ceremony, often hierarchical, usually involving blood, no backsies, no white gowns, no catering, etc. Then there is frequently some wailing about, I didn't get my wedding! And so then they have to have a regular wedding for everyone else.
Jeaniene Frost has pulled something I have _not_ seen previously. She created a no-backsies commitment and put her Fated Love through the ceremony in front of a whole lot of people. Then, in a later book in the series, she revealed that one of the parties to the commitment had _already made_ a no-backsies commitment to someone else. Sure, not knowing what she was doing. Sure, not knowing she had a fated lover out there -- actually, in a weird twist, she'd been convinced that by doing this she'd be able to avoid her Fate of luring vampires to their deaths and avoid her Fated Love, who she had been told she should fear. And _not_ as a full vampire, which made me think hey, we need Vampire Lawyers! Does Vampire Law even cover half-vampires? Does a commitment made as a half-breed apply when you mature? Really?
The solution is really obvious (kill Husband A, duh), and our heroine actually could have done this right from the beginning (nearly does, too, and has to go to a lot of effort to not-quite-kill Husband A) but does not. Instead, the whole thing drags on, she converts, she stops thinking of Vamp Law as nuts (wait, what? the effect of nutty vampire law is to convince people that it is not nutty, but in fact a good alternative to human solutions?), there's a duel, there is cheating (yeah, cause you couldn't see _that_ coming), etc.
I'm betting there is some weird analogy with early marriage, Southern Baptists, going to college, settling down with some Man Ho, discovering that what you _thought_ wasn't a real marriage, or what you _thought_ had been annulled wasn't, and then having to deal with some ridiculous divorce requirements in some ridiculous southern state, compounded by family drama, then compounded by an inheritance (or, say, successfully selling a couple of trashy fiction series) where there's some debate about how marital property works out...