Optimum and max altitude should increase during climb. Typically 4500-5000 lbs fuel burn(737-800) to TOC so OPT/MAX altitudes should increase by approx. 700'(before non-standard temperature issues).
But they don't.
The optimum alt on the cruise page stays the same throughout the climb until you are 1000ft from cruise alt. Thats not from a book, just from observation.