When does an analyst have enough data? An analyst never has too much data,........neither can you have too many motorcycles! The only limiting factors are (a) wife (b)money (c) riding time. My choices have been limited by those factors, but you can be creative to overcome (a), not so much (b). As for (c), I can always find the time, but not necessarily the energy to ride multiple bikes. At that price, I would encourage you to "add", and not worry about excess (or formula's)!