Do you rehearse your set from the middle, or always start at the beginning?

I’ve realised I know the first minute absurdly well because every rehearsal starts there. The dangerous bits are the joins halfway through, because they only get practised if I make it that far. Has anyone started rehearsing from random anchor points — begin at bit three, start from the closer, pick up immediately after a punchline — so the set isn’t stored as one long chain? I want to know the route, not need every previous sentence to unlock the next one.