I have a big rotation with a bunch of different sims. It's mostly comprised of my own sims or townies that I edited and added with some pre-mades, mostly from Get Together in my case. At this point, it's a few generations in, so it's more about the growing up children of the households I previously established. They are all going off in their own directions and figuring their lives out.
I have some dramatic soap opera households and some totally functional happy families. Recently I've been on a break but I plan to go back to it. Honestly, I have a lot of fun with my game. I set up a bunch of characters and it has all basically come together. When I consider starting a different save, I just end up playing it because I want to see where it goes. I guess I spent a lot of time developing my own characters, so they have their own personalities and quirks. At this point, they all have back stories and run into each other around the worlds.
I gradually edited the save so that I have numerous lots that are specific to my own game. I downloaded or downloaded and edited some but I've also built or created my own. I view the entire save as one integrated world. I have some rules specific to the different places in the game.
So basically, I've set up something that I enjoy. Sometimes I'll go in and build or edit. I also edit some townies that I want to keep and do my own culling. Sometimes I'll go in and build or edit lots. For example, I recently edited some of the bars to be more fitting for my sims. I added a pool to the Willow Creek gym and made the art gallery double as a wedding venue. I built a huge gym in Oasis Springs called Oasis Lifestyle Fitness with the Fitness Stuff pack. Those are just some examples. It's a cool game and I play it but I also take breaks and then come back.