I Second the Eireannach (Innuksuk).
Don’t know for average climbers, but for myself, if coming from sea level, 20 days would be the minimum. For people like me who are not willing to suffer much, I recommend a 30-day project, acclimatizing elsewhere (Cordon del Plata). This includes enough back-up days for the unexpected (weather, etc.).
Good luck to you who are headed south,
Ario