I do them, but just because, so far, it has not been my ridiculous to achieve.
This month went and drove 96 miles in total. Last month, 19k of calories burned. Previously, all three rings closed 25 times.
I've seen some horrible as average 80 minutes of training a day or the like.
Fortunately, I think the algos base it on your last activity, other people will have randomly difficult things to do.