I got all As for AS (and A*AAA at A2) just by cramming. For AS, each of my exams were spaced about 3-4 days apart, so I would spend the days between each exam cramming that particular subject, starting at about 5am. cramming. But to be honest, I did consistent work throughout the year, so I already was pretty prepared even before I started revising (My revision consisted of doing millions of past papers, memorising mark schemes and rewriting syllabuses). It was pretty intense but I work better under pressure lol. Up until a week before exams there wasn't much motivation to revise.