Normally for me I do it every 4-5 years.
It doesn't have to cost much, just wipe down walls, repaint (maybe even another new colour).
I like to change furniture, but because we don't like a lot....it's dead simple, and I always seem to have a Shabby Chic Look, because it is timeless and costs little.But I am thinking of getting close to a 'Hamptons' beach look next time...
Years ago people would keep it always the same, I have had friends who look like we are still in the 70's!!....That's scary.
Could not look at the same old thing year after year after year.
Even just painting, new curtains, and unclutter can make a world of difference.