Google Mail keeps 30 days of spam before automatically deleting old messages. Today was a milestone: my spam folder has more than 10,000 messages. More than 300 per day.
And this isn’t even all the spam I get! I get a couple dozen more spam messages per day to my direct personal e-mail accounts, and about a hundred a day to my work account. I’ve given up on managing it all. I don’t even check my spam folders for false positives anymore unless I’m expecting a message and haven’t yet seen it.
Charles Engelke's Blog 