is your car turbo? im going to go ahead and assume yours is. Im also assuming you know why you need the cool down time.
well if your turbo is ONLY oil cooled, then yes proper cool down time is critical. If your turbo is oil AND water cooled, and you have the water hooked up, then no, you dont need one, becuase the water is there for that.
Yes you can sit in your car for 1.5-2 minutes in your car leaving it idle, thats what the turbo timer does, thats fine. im opting to get the turbo timer, just to save me from sitting in my car with my eyes on my clock.
Im assuming you also know that with the turbo timer you know you can take your keys, lock your doors and s**t.