Plot hole: Josh is worried about the Quickening, where he has to have traditional sex with an uninfected person. Then, he realizes that he already had sex with someone while he was under the identity spell, which would logically mean that he already met the obligations for the Quickening and it should no longer be a problem. However, it persists as a problem until he has sex with Margo later on in the season.
Suggested correction: The quickening is tied to the lunar cycle and only happens every 30 years or so. And it's only in the 48 hours before the moon reaches its aphelion when the quickening happens, when the urge must be fulfilled. It doesn't matter what the infected person did before the quickening, the urge still occurs.
It was never mentioned that a lycanthrope had to pass on the curse within the 48 hours. It was explained that in the 48 hours leading up to the Quickening, all lycanthropes develop urges that begin with nightmares or waking dreams. Their condition is technically a curse that is driving them to have sex with an uninfected person or kill them, which would directly imply that so long as the curse is passed on, the needs are met, and the Quickening need not occur.
That's not what was implied at all. The Quickening is an event that happens at regular intervals that gives Lycans an urge that has to be fulfilled, regardless if they passed on the curse sometime in the past. Helen already passed the curse on to Josh, but she also experienced the urge from the Quickening and fulfilled her urge in the timeframe of the Quickening.
