The slower the twist, the less disagreeable the torque due to recoil, but the Germans long before the birth of the American Long Rifle had long barreled target rifles with very fast twists. The only set rule is that the ball must rotate 1/4 turn (25%) before exiting the barrel. Hence the British Baker rifle with a 30" barrel was made to that spec by rotating the ball 1/4 turn for its length, giving it a 1:120 twist rate. (They also thought it would foul less per shot allowing more shots before wiping the bore - good idea for a military rifle.)
From a 1/4 to a 1/2 twist is fine, so a 1:48 twist would give you a 50% rotation in a 24" barrel. But if you had a 42" barrel a 1:70 twist rate gives you a 40% rotation, also just fine.
LD