You're right that the majority of the material here is for picking up women. In general, this "don juan" site does not focus on maintaining long-term relationships.
The material I've seen on the topic seem to say the same thing: stick with what works. Meaning, if it worked for you to get the girl, keep doing it. Falling into routines can get boring and one/both of you may lose interest.
One of my best friends kept the interest level very high on his girl, going on 5 years now. It's funny because they have lived together for like 2 years now but he rarely sees her. They even work at the same company! (She is "obligated" to eat with her department) After work he's always out with us somewhere, drinking beer, playing video games, watching sports, whatever. I found it amusing one Sunday night, he said he had to go home early (~10pm) because he had to spend time with the girl. I was like, don't you live with her? She is a hottie, and they're now engaged.
He's not "spinning plates" or anything, in fact he doesn't have that many female friends, but what he does is the same result. He's always busy and his time is in demand, which is exactly the point.