As other's have said;
Down to Y11, I do a very long 3x3 wide tunnel (500 blocks to start), then from the beginning, make a 1x3 branch and I dig as far as I can go, usually 200-500 early game, late game with shulkers, I go until I have X stacks where, depending on my mood.
I space my branchs 3 blocks apart, very unlikely you'll miss any. Maybe 1 or 2. Nothing to worry about.
Late game I'll probably do 10-15 block apart