I noticed the difference immediately. My first Sinemet dose in the morning lasted much longer and when I took my first Stalevo thereafter (I alternate 1/2 Sinemet with 1 Stalevo 50) my constant jitteriness and hour-long dyskinesia just didn't happen! It was a smooth, virtually sympton-free ride till the dose started to wear off. But even then the "off" was much milder and could have been avoided if I hadn't waited so long to see what would happen.