How long is 2.71 hours?

It is exactly 2.71 hours.

If you mean how long is it in minutes, then 2 hours are 120 minutes and 0.71 hours = (0.71*60)=42.6 minutes (and 0.6 minutes = (0.6*60)= 36 seconds).

Therefore 2.71 hours = 2 hours 42 minutes and 36 seconds, OR 162 minutes and 36 seconds, OR 9756 seconds long.