Why do esters have to be distilled during purification? I am currently designing a lab experiment for a school project in which I am to determine the effect of catalyst concentration ($\ce{H2SO4}$) on the rate of reaction between methanoic (formic) acid and ethanol to create ethyl methanoate. I plan to do this by varying the concentration of sulfuric acid at the beginning, and comparing the end yield of ester.
$$\ce{HCOOH +C2H5OH &lt;=&gt;[varied concentrations of H2SO4] HCOOC2H5 + H2O}$$

I am aware that distillation is a crucial step following reflux in pretty much every esterification for purification, but why? Can't one simply wash the crude ester with deionised water to catch all remaining ethanol, use CaCO$_3$ to neutralise the acids, and filter off via a separatory funnel? 

I am asking this because my school project has a set timeframe for all experiments of officially 8 hours over two weeks, in which it is recommended that I conduct at least '5 measurements at 5 intervals'. I know I won't reach this, even if I reflux each of my esters for 10 minutes because of the distillation.
According to Wikipedia ethyl formate is 9% soluble in water, that figure may be increased by any excess ethanol present, so you will be losing a significant portion in the proposed work-up. Is this enough error to invalidate the experiment?