Startup CEOs heading to the public markets have a love/hate relationship with their investment bankers. On one hand, they are helpful in introducing a company to a wide range of asset managers who will hopefully hold their company’s stock for the long term, reducing price volatility and by extension, employee churn.

On the other hand, they are flagrantly expensive, costing millions of dollars in underwriting fees and related expenses.

Worse, the advice one gets from investment bankers tends to be quite vague. There is all this talk of IPO windows, timing, pricing, and more that is so squishy, particularly for the sorts of Silicon Valley CEOs that prize data over human experience. That has led to more than one experiment to try to disrupt the investment banking sector and the whole going public circus.

Uber and Lyft though are proof though that investment bankers actually are pretty smart in their advice about the pubic markets, and founders should be cautious about ignoring their words.

Let’s look at a few case studies.

First, take the vaunted “IPO window” that is discussed ad nauseam among investment bankers and the financial press which covers them. The idea of the “window” is that you must time a new public equity issue to arrive at a propitious moment in the markets. You want investors who are hungry for growth, and not battening down the hatches preparing for a recession.