^^^
It is far more common for the valve lash to decrease (tighten) with time on the engine because the valve faces get hammered into the seats by combustion pressure, and thus, the gap between the valve stems and rockers (the lash) decreases. Having the lash increase is far less common. It's strange that your experience has been so different, however - maybe yer car's just freaky like that?!?!
And as far as Kenik measuring/adjusting the lash on a time interval regardless of engine use, well, I can only conclude that he is certifiably insane!
Also, Rahl, you are correct that many people on Pelican measure/adjust valve clearances when it is entirely unnecessary. Like all engine manufacturers, Porsche specifies a variance of plus or minus .002" in clearance - in other words, quite a bit of range.