You should always wait until 15 minutes has passed before voting, or else the curation rewards are being wasted / returned to the reward pool.
The point is that there is no need to wait up to 15 minutes. The curation formula also takes into account other factors. And @nfc therefore votes earlier, because it is more profitable for him.
Alright, that's fair. I didn't look into his curation efforts, I was just assuming it was someone who wondered why it was "bad" to vote early. And I think that it might still not be a good idea to vote very early unless you know what you are doing.
Yep, thats true, but I think @nfc knows what he is doing very well :-)