Comoso, my situation was a bit different because I was switching from Cymbalta to Lexapro, so I was all whacked out for at least a month. But with Lexapro I would say 2 months, maybe even 3, until I noticed a change. I am sure it happened gradually but it wasn't until I faced a more challenging moment and had a better reaction that I could really say that it was doing something.
I am not off the Klonopin though. I have been on and off it for 20 years. I am stable on .75mg a day but if I need more I take it. It's just a choice I made that I am okay relying on it. But before Lexapro I was taking 1.5 a day and I cut back to .75 within about 2 months of feeling better.
.5 isn't very much (that you are on), what are your concerns with being on it?