Short, frequent sessions beat occasional long ones. Five to fifteen minutes most days, targeting the two or three areas that genuinely limit you, produces steady change. Mobility work also fits naturally into warm-ups and rest periods.
Range of motion responds to repeated exposure more than to duration in a single session. Five minutes six days a week gives you six separate signals; thirty minutes once a week gives you one. The first approach produces more change and is easier to fit into a life.
Running through a fifteen-drill routine covering everything is how mobility work gets abandoned. Test yourself, find what actually restricts your training, and work on that. For most people it is ankles, hips, or the thoracic spine, and rarely more than two of them at once.
Follow a mobility drill with a strength exercise that uses the range. A couch stretch followed by glute bridges, or thoracic rotation followed by half-kneeling presses, converts temporary range into range you can control.
Two to four weeks for the sensation to change, six to twelve weeks for measurable range change, and longer for it to hold without ongoing work. Retest every four weeks with something objective, such as a knee-to-wall measurement, so you know whether it is working.
If a joint feels irritated after mobility sessions, or you are stretching aggressively every day without any change, more is not the answer. Reassess whether the limitation is really about range at all, as discussed in The Joint-by-Joint Approach to Movement.