I find the evolution of the Little Pinto/Lucrece Posey romance in the stories very interesting. There was originally no intention to make their relationship anything more than superficial on Lucrece's part and accepting of this on Pinto's part.
But I do have a deeply buried romantic side, and it tends to flare up whenever any such relationship is enacted in my presence. If one of the characters loves for real (and especially if I adore either the character or the actor), I have the desire to make it real on both characters' parts and get a little squee going on.
Hence, the more I wrote their scenes together, the more I started to fall in love with the idea of the pairing being genuine and the more I wanted to see if it could happen. I wrote an experimental oneshot that takes place during The Night of the Poisonous Posey, after Pinto's death, and then decided it could work. I started implementing scenes in the Time Travel story to explore the idea that Lucrece loves Pinto, but is denying it to herself.
It's a very gradual process, with Pinto starting to realize the truth long before Lucrece is willing to, and even after she starts to, she can't bring himself to admit her love in outright words until almost the climax.
I had toyed with the idea of her not acknowledging it until the climax, when Pinto is nearly killed by Snakes Tolliver, but I decided it would be too cliche and not nearly as powerful as the idea of Lucrece acknowledging her love in a relative time of peace instead.
Currently, in the third installment The Night of the Deadly Codename, they are making plans for their wedding. And unbeknownst to them, their modern-day descendent is roaming through Los Angeles. He is aware of them and wants to see and talk to them, but figures he cannot identify who he really is.
Something else that changed is their attitudes in how they display their affection for each other. When my concept was only for a superficial arrangement, I imagined it would be quite sultry and that they probably wouldn't care if they broke social morays of the day and fooled around in the bedroom. (Not that I would ever write such scenes even if I imagined that's what they were doing.)
As I watched the episode more, however, and also began developing my ideas for genuine love between them, I softened their physical displays. Note the difference in their reunion scene in The Night of the Lazarus with their scenes in Time Travel. Perhaps there's still some hint of the sultry in the latter, but once Pinto is able to get through to Lucrece that she really does love him (even if she won't say it), they don't need those overtones anymore---whereas in Lazarus, the physical is all Pinto thinks he can get with her, so he takes it.
I also decided, however, that they most likely have kept their relationship out of the bedroom, even during the time prior to Time Travel. Although it's never outright stated, I have made deliberate hints to that fact. Lucrece notes that she has not seen the healing scar on Pinto's chest since he showed it to her to prove himself as the real Pinto, indicating that she has not again seen him with his shirt open, let alone off. And as they discuss when to marry in relation to when to move, Pinto says that if they marry first, they'll need one less room, since they'll be sharing one. This indicates that they are saving any sharing of a bedroom for after they're married.
One of the things that fascinates me the most about Pinto is that in spite of his sadistic nature, he really can be quite the gentleman. He is the only one other than Brutus to stand when Lucrece comes in, and he is always the one to pull out her chair for her. So it started coming to me that perhaps Pinto would wish to be gentlemanly with Lucrece in other matters as well, including how far to take their relationship while they're not married. Coming from the Victorian era, he does not want to taint Lucrece or encourage her to engage with him in acts that could shun her in proper society.
(Of course, that begs the question of why they would think it alright to pursue their current career path, but since when have criminals always made sense? They contradict themselves all the time.)
As to whether Lucrece could have already engaged in such acts while deceiving various men, that is better left up to the imagination. At this point, I honestly have no idea.
Although I would be inclined to say she hasn't, and that sooner or later that could end up addressed by way of a passing comment in one of the fics.
In any case, the relationship between them has definitely been one of the subplots I've enjoyed tackling the most. While they are thoroughly criminals and that will not change, they somehow truly do love each other. It's fun to bring that out.