I'm glad my answer helped so much :)
It's difficult to estimate how long it'll take on average, because there are so many variables to consider (eggs per day, luck, Shiny Charm etc.) But I'd say you're pretty lucky to have a shiny in a week, of course depending on how often you hatched eggs in that time. Statistically, it isn't unlikely for it to take hundreds upon hundreds of eggs to finally hatch a shiny, so depending on how quickly you hatch eggs, it could easily take months. Again, it's difficult to make any accurate judgement; personally, I prefer to simply let the terrible odds speak for themselves.