I have used the same Gmail address as my main email for over 5 years. Since then:
As a result, my Gmail account gets inundated with email. Here are the stats:
My Gmail account had become a firehose.
This was bad for two reasons.
First, I started missing important emails. Not many, but a few per month. I had to write my own simple Bayes filter to find them.
Second, I couldn't do what most people do: use my inbox as a "todo" list. Most people immediately archive or delete an email when they're done with it. This is a great organizational trick. I wanted to do this again.
I considered starting a new email address and giving it out to important people, but that seemed like it would make my life more complex.
As it turns out, the solution was simple.