Journey time calculations in Google maps, Uber etc. mean no one I know is ever on time. If you need to be somewhere at 8:30 and the journey “takes 17 minutes”, one psychologically sets 8:13 as the deadline for leaving the house. You pick up your keys at 8:13, actually leave a few minutes later, hit traffic or take a wrong turn or two, and end up crossing the threshold at your destination fifteen minutes late. It’s no…
Google's estimation for my country is always less than what is achievable if you stick to the speed limit. I guess they calculate it based on other drivers.
Eg if you have a 100 mile drive on a 70mph road and you drive the entire way at 85mph your reward is saving about 10 minutes on a 1.5 hour trip.
The downside risk is getting charged for speeding and being delayed for much more than 10 minutes.
I've never though the cost/benefit shows it to be particularly worthwhile.