There are lots of stories on this forum from people who found they needed more than 90 days. (And a fair number who needed less than 90, too.)
I did 100 days and noticed some improvement, but I wasn't fully cured. Lots of things had changed, but I wasn't back to how I was before porn.
I'm doing another 100 and then will think carefully about my progress. The longer you've held off, the less worrying it is to increase the duration. When you start, 1 days seems impossible. If you make a week, you start counting the weeks. After a month, deciding to wait an extra few days isn't an issue. After a year I expect one month more of less isn't bothersome. It has become a habit.