I opened my Gmail account on January 4, 2005. 69,963 emails later, I hit the quota of 7.6 gigs.
Today, I received a note that the account is almost full:
95% fullUsing 7222 MB of your 7601 MB
I just splurged for an extra 20 gigs–effectively quadrupling my quota–for $5 a year. Good deal.