OD&D describes ghouls thus:
As stated in CHAINMAIL for Wights, Ghouls paralize any normal figure they touch, excluding Elves. They otherwise melee in the regular fashion and are subject to missile fire. Any man-type killed by a Ghoul becomes one.
Even if you don't usually treat OD&D's requirement of Chainmail as an absolute prescription, the explicit mention in the ghoul description is strong. The Chainmail entry for ghouls (and wights) says:
If they touch a normal figure during melee, it becomes paralyzed and remains so for one complete turn. A paralyzed figure is considered to be able to strike a blow at the Wight just prior to paralysis taking effect, so melee can occur but only one round.
Chainmail page 8 says, "one turn of play is roughly equivalent to one minute of time in battle"—the same duration as OD&D's combat round.*
It seems clear to me that the touch/hit of a ghoul leaves a character paralyzed during the following combat round, and only that one round, regardless of saving throw (if you allow one). This makes ghouls considerably less deadly than under other interpretations, even if the party doesn't include an elf.
Update: Upon further review of Chainmail turns and rounds, I realize ghoul paralysis lasts longer than one OD&D combat round. However, the ten minute "exploration" turn mentioned on page 8 of U&WA is far longer than Chainmail meant ghoul paralysis to last. The more I look at Chainmail with OD&D, the more I think combat turns should be one minute, with rounds of perhaps 6-10 seconds.
* Yes, yes. Turns and rounds are another point of contention, but regardless of specific duration the Chainmail turn round is "one exchange of attacks," as the OD&D FAQ describes combat rounds.