Goodonyer Bloggs,
If you've got accurate route winds and temps in the FMS and it says go up, go up!
Such blind faith in a box (in your jet) that does not even take into account the aircraft bleed status, relies on a predicted capability of only 100 fpm for max altitude, has no means of temperature prediction and has no installed limitations for manoeuvre margin between low and high speed buffet boundaries... but then, you were trained by the "it's OK to let the feet cross" experts, if I remember correctly.
Ask Clarrie what happens if you follow your advice...
I had hoped you would have said: "know the limitations of what and how the box calculates things, because it accepts no responsibility for the outcome"!
Stay Alive,