I have a 3.5 year old Sony RPTV. I tweaked the convergence about a month ago - everything appeared as good as could be. I checked it last night -- the red had drifted significatly on the top part of the service menu crosshatch grid. Why did this happen? The TV has not been moved or touched. Could temperature change have done it? I have done comparisons like this before and never saw this much of a difference. Maybe I should tweak my convergence every few weeks so things stay optimal.