Just thought I'd mention an exception to the 10-ish years rule. The new Nick Cave album "Skeleton Tree" is really freaking heavy! It might not be quite up to Birthday Party standards, but it's definitely worth checking out if you like dark music.
it really is hard to maintain an edge when you have millions of dollars in the bank. With most bands that have longevity they just lose their edge. They have nothing to be angry and mad about anymore. They aren't scratching and crawling to the top anymore. I think you see this all the time.