I was always curious how I fit into the usage curve - as of this moment, I have 17,849 notes with about 380 tags since April 9, 2010.
I would estimate 50% of my notes come from my web clips or forwarded emails from my inbox.
At the rate I'm going I might hit the max. in 10 years - but that is not that far off. I figure by then the underlying Evernote database technology and certainly the underlying Evernote infrastructure will change and remove those limits. I put a lot of pictures I want to keep a long time into Evernote - would like to add video, and I'm sure that would really bump up the storage needs - my guess is that Evernote will hold off on video storage for some time.
I actually refer to my Evernote as my external brain pack. (Kudos to Dilbert for the term).
Keep up the great work Evernote!