I use my Flickr account as a kind of journal of my journey through photography. That being said, I only upload things that I consider "keepers" (at the time of upload), so after two years, I now have 629 shots there. (I don't understand people who seem to upload every single shot.) I don't often go back to see my oldest photos, and I don't expect many of my contacts do either, but it's fun to go have a look once in a while to see how my eyes see those older shots now. I also try to keep a reasonably current album with a
Top 25 Most Interesting to make it easier for people to find the "Good Stuff", as well as other albums like a yearly list of favorite shots of that year. I think if I were to invest the time to upload to other sites (such as 500px), I might only upload there a small subset of my Flickr photos...