The chapters costing you marks are rarely the ones that feel hard.

Not by instinct. Take your last three or four mocks, tag every wrong answer with its chapter, and count. The chapters at the top of that count are your weak ones, and there are usually far fewer of them than it feels like — most aspirants find five or six chapters carry the majority of their loss.

Weak chapters first, but only the ones that are actually costing marks. A chapter you are weak in and that never appears is not worth a fortnight; a chapter you are slightly wrong about that comes up every year is worth two.

About two weeks of honest work for a genuine conceptual gap: relearn the concept, work through problems until the method is automatic, then retest cold after a gap to check the correction held rather than just felt convincing at the time.

For a conceptual gap, roughly eight weeks out is the honest cutoff for starting a chapter from scratch. Inside that window the better return is on accuracy and mock analysis — the marks you are already earning and handing back are recoverable much faster than new syllabus is learnable.