Valve Job
Me thinks you have confused the valve adjustment, with valve job. A valve adjustment is adjusting the clearance between the rocker arm, and the valve. This is a fairly simple operation, and the 200 hours for the first one sounds about right. I would recommend this procedure be at least checked at around 1000 hours max. after the initial adjustment. A valve job normally means to pull the head, and grind/reseat the valves. As far as I know, there is no recommended time to do this, just as needed. BUT, if you do not adjust the valve clearance, then you may very well be doing a valve job much sooner.