I want LS but question romance decline

It seems to be a bit random if and how much romance declines. With my main couple, it's sometimes down by maybe a third when I get back to them (I play rotational), and if that's the case, I send them on a date and have them do romantic stuff. What works really well is including a few romantic gestures throughout their day. That helps the bar remain stable. Also, if traits and interests align, the decline isn't all that bad, if it happens at all. 

I have one couple that has never had the romance decline at all; with another couple, the bar was almost empty when I last played with them. Sending them on a date and have them interact helped a bit but in their case I didn't worry all that much. After all, they just had a kid, of course they would be stressed out and not have much time for each other.

What's interesting, though, is if you have a couple that's not a good match at all. When Lovestruck came out, I created a couple that was like night and day - he's a criminal, she's a lawyer. He hates kids, she wants a bunch. He is nasty, mean, and everybody hates him, she is lovable and has tons of friends. In short, I set them up for failure because I wanted to test the gameplay that came with Lovestruck, like the marriage counselling. Also, I didn't put in much effort once that romance bar started to decline because I wanted to see where it was going, then decided I'd let it spiral into a full-fledged drama including a divorce.  With another couple I created to test gameplay, the husband changed from super-shy to super-romantic while the wife became more and more reserved and eventually developed a trait that requires forming a stable friendship before she even considers flirting with someone. Again, these two weren't a good match; they, too, are divorced, and the wife is now dating Caleb Vatore :D

In short, the romance decline seems to be random and linked to a couple's traits and interests. The better the match, the more stable that romance bar.