When I build, I spend however much time on it as it takes me to feel bored or frustrated, then I move on. I also switch tasks—building/doing floors and walls/choosing furniture/recoloring furniture/landscaping—as I feel like it and whenever I get an idea for something else I want to do. Usually I'll at least place some furniture while I build so I can make sure the layout works, but other than that I do whatever I feel like doing. This is supposed to be fun, after all.
As far as being in a rut, have you tried just jumping into something without a plan? When I got Dragon Valley not quite two years ago, I loaded it to test something else because I wanted to see what it was like. I picked a random household and ended up enjoying the sims so much that turned into a save I played for a while. Then I decided I liked the town's other sims so much I wanted to play most of them too, so I started a new save there and made it over 50 weeks before leaving off a couple months ago. (I still plan on going back; it's just that haven't been playing computer games in general these days.) It's been a totally different experience than my normal playstyle and a lot of fun in its own right.
Point is, if you pick something random and go with it, maybe you'll find you enjoy it even though it's not how you'd normally approach the game. And you might end up using interesting features you normally ignore.