What to do with long equation-heavy solutions?
This happens not just in mathematics but in many other disciplines as well: modeling of biological systems, for example, often involves a vast number of terms in the equations.  The best approach that I have found for these sorts of situations is to look for the structure in the system and to build your presentation around that structure.

In most cases that I have encountered, it is not true that there are simply a bazillion essentially unrelated terms.  The true story of the equation, then, is not the expanded mathematical form but the process and relations that generate it.    This opens up a number of approaches for factoring out the equations in order to make them more tractable to present, including:


Abstracting sub-structures as variables (e.g., X^2+XY+Y^2, where X and Y are complex terms presented separately)
Separating variables from parameters (e.g., a reaction network where each reaction uses one of several standard Hill equation models, with the parameters of the models presented in a table)


These sorts of factorings also lead to a much more informative and interesting presentation of the equation as well.  In fact, the Big Equation itself may often end up being relegated to an appendix, where its page-busting form is of little concern.

There may be, of course, certain systems in which such factoring is impossible---and that fact is quite interesting and worth clear discussion!