Started learning just after 17th birthday. Finally passed third test about 18 months later. Had a lesson once a week, but never allowed to drive anything else. My 3 brothers all got taken out several times a week in addition to weekly lessons and they all passed first time. Dm still talks about what a rubbish driver I am.
Dh started at 17. Had weekly lessons for 6 months, but hated the instructor who kept chipping at his confidence. Gave up learning until he was 25 or so and then passed after another 6 months or so, but he was much more comfortable with it by then.
As others have said at some stage it just clicks.