My philosophy has changed over the years. I used to do 20% every week or two.
Once I got a 7 gallon tank that I wanted to try acros in, I was doing half a gallon a day or every other day. It could be done in a few minutes and really helped establish a routine. Surprisingly, it was the most success I ever had with acros.
When I went to a 20 gallon, I was doing water changes every week, sometimes twice a week.
I think going forward for tanks between 20-75 gallons I would do water changes twice a week to try and build a better routine.
For tanks sub 10 gallons or maybe up to 15, I’d do them every other day.
Eventually I want to do a 250g+ build and my goal is to try and create a tank where I can do very infrequent water changes but that build is still a while away.
I think the biggest perk of doing water changes very frequently (multiple times per week) outside of stability is building a regular routine. If you do them every two weeks, it’s easy to skip one. By doing it every day or every other, you’re doing something more manageable on a regular basis.