I've experimented with many benzodiazapines in my time. But Clonazepam (Klonopin) I would have to say is the longest lasting of all of them.
At approximatly 7:30 am I swallow a .5 mg Klonopin on my way to class. It doesn't take long to start feeling the effects and by about 7:50 am I am already feeling myself 'Come up' on the drug. I can feel a tingling sensation on my head and I have no worry in the world. By about 8:15 pm I can already feel myself peaking off of the drug. I feel slightly euphoric, and all of my movements are over-exaggerated, alot like valium or xanax.
During this time I am in my chemistry class taking a test. Suprisingly I am able to focus on it and finish it but I feel rediculously fucked up and still able to enjoy the feeling of the drug. My speech wasn't slurring but I felt like I was almost to that point. My teacher calls on me to ask me a question, and when I look up it feels like the world just flipped upside-down. I would have fallen out of my chair if I wasn't holding onto the table, but miraculously I answer her question and there was no suspicion of my intoxication.
I go through the rest of the day like this, with only a few people noticing me acting a little different. The drug itself was very pleasing, it felt like the effects of a skeletal muscle-relaxant mixed with an opiate like hydrocodone. It lasted all the way up until I went to sleep at around 11 pm. The only downside to this drug that I see is that it is very hard to recall what happened during the time I was on the drug due to amnesia being a common side effect.
Minor effects of the drug still felt the next day. I wish I could tell more but it's very hazy.