Share your experience here, but please understand that everyone is different. For someone who eats a fairly low carb diet to start with (30% of total calories from carbs or less) it might only take 5-7 days.
However if you have spent 30 years or so eating the typical high carb diet, it may take anywhere from 7 – 12 days. Be patient and make sure you stick exactly to the program for the first 14 days. Once you are in ketosis and your body becomes fat adapted, (burning fat as it’s primary fuel source) you are able to have more flexibility.
How many grams of carbs per day to keep you in ketosis can also vary depending on body weight and the amount you exercise. For someone who exercises 5 x a week and is 90kg (198lbs) they might be able to get away with up to 70g per day. The KETOFAST plan is based on 30-40g per day which is a safe amount to ensure you get in and keep in ketosis.