Mientras

[Perikles]

The nature of the actions and their coordination make it work as if it means "until", but the way the sentence is laid out suggests the author may have intended to say they avoided to make making any noise until the last second and they woke up the driver just for him to perform his duties, or they stretched the period of intimacy by letting the driver asleep (or any of thousand plausible reasons)Thanks Alec, that is how I understood it. :)

[Cloudgazer]

Thank you, Alec. The phrase's context seems to make this reading of the sentence unavoidable, but I see what you mean. If the driver is ever awakened by them, it has to be after they get into the seats. ¿Pero no podemos tener algo como: "Y no lo despertaron mientras no estuvieron instalados en los asientos. Una vez instalados, al ver qué tranquilo el chofer parecía, decidieron dejarlo dormir y salieron a ir a pie."?

[aleCcowaN]

¿Pero no podemos tener algo como: "Y no lo despertaron mientras no estuvieron instalados en los asientos. Una vez instalados, al ver qué tranquilo el chofer parecía, decidieron dejarlo dormir e irse a pie."?
In everyday Spanish this paragraph is acceptable, but for literature it should say "y decidieron no despertalo mientras no estuvieran ..." or "y no lo despertarían mientras no estuvieran...". The use of indicative tells that both actions will be fully performed in the end -despertar and estar instalado-.

[Cloudgazer]

Gracias de nuevo, Alec.