The 2nd Edition codex came out in 1996.
The 3rd Edition codex came out in 1998.
The 4th Edition codex came out in 2007.
The 5th Edition codex came out in 2010.
We are now over two years into this book and it has proven to be a pretty balanced book. However, I wonder how long until we will be looking at a new book.
Although they have had a codex every edition, this pattern might end. Templars, Dark Angels and Space Wolves have all missed an edition previously. I doubt they will let the Space Marine / Ultramarine codex miss an edition, so it could be the Blood Angels' turn to sit one out or be released with 7th Edition in mind. Let's hope that GW increases the pace of codex releases so the Blood Angels don't end up left behind like Templars or Dark Angels or even worse - Xenos codices!