Various opinions on this one, and it also depends on what went into the fermenter, besides wort!
I've filtered my wort thru a straining bag and I get a very clean wort so when I harvest yeast its really white. No need to dump trub.
I've not filtered, had lots of hops, failed to dump within 7 days and it was packed up pretty good. Another time, one of the first times with a conical, I didn't dump for 2 weeks. It was packed up tight! Not good really.
So, it all depends, but the main thing is if you do dump some trub, you don't take off too much too early, lest you potentially halt fermentation.
While this is late for your Q, but I've heard of guys who fill the fermenter, let it rest for 1/2 to 1 hr, dump trub, then pitch yeast. I like this approach, along with straining.
Finally, remember to remove your air lock first! Don't want the water or sanitizer you have in there sucked back in! Oh, and sanitize your valve outlets well before and after.
