How Often Do You Redecorate Your Sim's Houses?

I do it pretty regularly. Just small changes to decor literally all the time, every few Sim days I'll tweak this or that just for a change of look.
Entire renovations to rooms or even entire floors also happen pretty much every time there's a change to the household, be it a change in the age of children or the career/skill activity of an adult.

Toddler ages up to child, for example, their room gets an entire renovation in furniture and decor and any area that were set up with toddler activities gets a full renovation with child stuff in it's place. The same happens when a child ages to Teen, or when any adult makes a change in their career/skill.

I don't generally live on giant lots with massive houses, so renovations are needed when anything changes in terms of what kind of 'stuff' I need available in the house and it's just a good excuse for redoing decor along with it.

Kind of depends on the family, sometimes I will put away everything in storage that people might be attached to and then match things together they would want. Which could be at any point such as getting a promotion or saving enough in the household funds. Other times if one of the kids will keep the house I might change every room they would spend time again and decide what they get as they have their own kids.

I must admit I hate redecorating. My poor Sim kids often don't get anything that suits their age. I mostly just squeeze the necessary new items in somewhere, though I always tell myself I will properly renovate after the next birthdays, wedding or death.

I rarely completely renovate the whole house all at once unless some really major change happens, like more sims moving in.

But I am constantly going in and out of build mode as I play to make adjustments to the placement of things, add an additional room, add new items, or remove items, as their needs change. And I make whatever aesthetic changes I want to make as they get more money, like adding curtains, or a nicer wallpaper. So the house is just sort of slowly evolving over time rather than being completely redone periodically.

If I do want to make major changes (such as building a whole second structure on the lot, adding a lot of additional rooms, renovating the yard, or majorly changing the main function of an existing room) I often do it in stages, interspersing the build sessions with continuing to play the story even if there is enough money to do it all at once. That way it's like the new place is actually being built, the way it would be in real life, and the sims can go check out the progress as it takes shape over the course of several days or weeks. The renovation becomes part of the story that way.

I renovate all the time esp when I first move them in to a new apt or then the home they eventually move into. As the family grows so does the house so it has to get add on rooms or makeovers to accommodate their needs, plus I love to decorate or create homes.

Whenever the way it currently looks becomes distracting to gameplay.
"Hey, I don't have a toddler bed and now I need one"
"Hey, Grandma's room probably doesn't need to be kept the same way so long after her death"
"Hey, this couple is middle-aged and reasonably well-off, their apartment shouldn't look like the apartment of two penniless 20-somethings who think bar decor on the wall is funny"

I'm pretty fussy with houses for playing in, so when I find one I like and start playing with it I usually keep it as it is, unless there's anything that absolutely needs changing for gameplay like changing from a toddler bed to a kids bed. Then when I get bored of a house I just move

Another reason why I'm considering re-decoration is because my sim self's wife has been lately showing the sofa with a cross through it thought bubble indicating she no longer likes the furniture!

"Brd709;c-18037357" wrote:
Another reason my I'm considering re-decoration is because my sim self's wife has been lately showing the sofa with a cross it thought bubble indicating she no longer likes the furniture!

Oh, that's a really good reason to redecorate! With the how Sims now have a preference for style of furniture, it's something I'm still getting used to myself.

Annually or by season, or by plot. Usually by plot.
I think of my houses like stage sets.