Is it ever too late?
No. The "set point" doesn't become more entrenched over time. Habits might, but research has shown us that habits can be changed. People who smoke all their lives are able to quit. There's no reason this should be any different. Why do the methods you describe work?
They're creating little bursts of enthusiastic feelings. And really, the key to having lasting happiness is having frequent positive emotions. It's unfortunate that so many people poo-poo feelings on the basis that they're transient. Even though they're transient, they're perhaps the most important factor in getting that 40 percent of happiness under our control. Are you happy?
I'm up there, but I don't live enough in the present. I have what we call "future nostalgia." I'll be sitting on the couch with my young kids, thinking that they're wonderful. But then I can't stop myself from thinking about how they're going to change; they'll be getting older soon. So, I'm already expecting to be nostalgic for that moment, rather than savoring it. Like anyone else, sometimes I need to heed my own advice.