I don't double clutch, also have never replaced any transmission parts on my manual transmission cars (except I added a short shift kit to the impreza, but that is more for me than the car), that I have bought exclusively since replacing the automatic transmission on an older Honda accord, that cost more to replace than the car was really worth.
But I also don't drive my car like it is a racecar, maybe that is why everything stays in workable condition? If I keep the Impreza for 10 years, maybe I will be replacing the clutch...is 150,000-200,000 miles of wear acceptable on the original clutch?