After taking Klonopin it takes around 1 to 2 hours at most to peak and for you to feel the effects of the Klonopin.
So you should begin feeling the effects within 2 hours after taking Klonopin and then after the Klonopin peaks it can start to wear off within 8 hours.
So you may have to take some more Klonopin after 8 hours if your doctor has told you too.