Oh, where to start!? I feel playing this game is like living a double life, not only for one household, but I play a full community including laws, nobility, stock market, council with 5 years elections, and I keep track on every individual cash account. I have so many plans for my community, but not enough time to do it all, even if I recently spent way too much time on it. It includes lots of organizing, scripting and reporting, too, as I base most of my youtube videos on real sims and locations in my game.
I am into programming, so when I think a registry with info we don't access easily in game would be useful, I create that registry. On my blog simmerville.blogspot.com there are links to the Residents Registry, Community Section (split into the Councilor's departments Law & Justice, Trades & Taxes, Culture & Entertainment, Health & Welfare, and finally Education & Science.
I've currently built a site where I can look into each nobility house's jewelry box. I needed that to keep track on what Duchess owns what necklace and tiara, because it would break all my illusions if a low nobility lady shows up wearing the Duchess' tiara, right? I wish we had personal dressers and jewelry boxes in game... (btw, the jewelry box site is not yet online, will be in a week or two).
My rotation includes 60+ households, might soon be 70. I play each house for only 1 day every other year, but if something exciting is ongoing, I can easily stay 5 days with one house, and skip a few unless they have birthdays etc. So, although the amount feels massive, I make sure to be flexible. Sometimes I even play a full year without anyone aging, just to get the time to focus on specific features, like when I want to enjoy a newly added pack.