Tick Tick Tick sound from valve train....

[HuskyMan]

OK, here's the history on the 1984 300DT. approximately 5000 miles ago, I installed a valve stem seal kit and installed new valve springs and then performed a valve adjustment while the engine was cold. A "metallic tick tick tick" sound was heard afterwards.

So, I took the car to a mercedes factory trained mechanic who suggested that I readjust the valves with the engine hot. I did what he said and the noise disappeared. The engine has been fine until last evening when I opened the hood and listened to the engine at idle. It sounds as though the "metallic tick tick tick sound" is back though not as prominent. Is it possible for one or more valves to go out of adjustment after only 5000 miles?