Well, I have a pale ale bottle conditioning right now, and I took a sample from the fermenter at 2 weeks and again at 3 weeks (bottling day). It was somewhat clearer at 3 weeks, but more importantly, it tasted noticeably better. YMMV, and it hasn't bottle conditioned yet, so who knows maybe it will taste like crap after all
Anyway, the extra conditioning time is not
just to let the yeast flocculate and the beer to clear, it's also so the yeast can break down more stuff, like the more difficult-to-ferment sugars, the waste products they generated previously, etc.
Of course each individual brewer must decide for themselves when each individual beer has fermented long enough. There are no hard and fast rules. I have a summer wheat beer that I am hoping to rush out of the primary a little on the early side, if the yeast will permit, because I am more concerned about having it ready to drink when it starts getting really hot outside than I am about having this one be the perfect beer. (I have others fermenting now that I would like to be "the perfect beer", this one I'm just hoping to have something thirst quenching for a hot day
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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As far as your airlock question... I would probably clean it out and refill it, yeah. If you don't have another airlock that you can have on deck and ready to go, you can put sanitized aluminum foil over the top while you are cleaning the dirty one.
That said, I've got an airlock that had some yeast blow into it, and actually this will be like the third frikkin' time I've cleaned this airlock because I keep thinking it is done blowing off and then it's not. I should have just put the blowoff tube back on it, but what do I know. Anyway, I've just left it there for a couple days and I will probably finally replace it with a fresh one tonight or tomorrow. The main concern, I think, is not so much sanitation, but that it could become clogged and blow your lid/bung off.
If there's enough gunk in there you think it might clog, definitely clean it ASAP. Otherwise, well you should probably clean it anyway, but I don't think there's a rush.