There’s no hard and fast rule; generally speaking, the more often you wear your denim jeans the sooner you can expect to see results. A good estimation is anything from six months to over a year. Seeing fades and impressions are a good start. Over time, expect more whisker marks behind the knee area and some impressions at the pocket area where your phone or wallet usually sits.
With more wear, the jeans should feel like second skin as you slip them on. No, it’s not a substitute for pajamas.