Why do financial models become more complex? Have you come across the situation where after doing the complex calculations you realize that it is of no use? Should you include everything all kinds calculations, balance, permutation / combinations without knowing the end goal of the model?

It took Fred three months to build his first model, needless to say he didn't get lot of sleep during those periods. The second model, Fred started, though a different business, large parts of the model required the exact same logic as his previous one, and same for the third one. Should there be a universal template which consists of all the logics he needs very frequently?

A financial model is a tool to put theories/predictions to test, a financial simulation to measure suitability of a transaction or a reporting tool to get insights into business performance.