Newbie yeast question

I brewed a red ale on Friday, pitched yeast at 5pm and then added an AHS add pack (corn sugar, maltodextrin, and yeast hulls) around 4 hours later. I woke up the next morning to a VIGOROUS fermentation.

By Sunday morning it had slowed to almost a halt and it appeared to have completely finished fermenting on Sunday evening around 7-8pm. I let it sit until yesterday (Monday) morning when I sat and watched it for a good 3-4 minutes straight and witnessed zero bubbles. So I took a gravity reading at 1.010 down from 1.047 on Friday night.

Is that a normal ferment? ~48 hours with only 15-16 hours of rapid fermentation?

Yeast used was Windsor Ale Yeast (00393) and I rehydrated it in water ~75-80F that had also been used to steeping (I ladeled some of the steeping water out and used it to rehydrate yeast, since it was already ~170F thus sanitary, and let it cool to 80 before rehydrating). The yeast stayed in the warm water for about an hour before I actually pitched to the wort (5pm).

The AHS "add pack" I totally forgot about adding during the boil as I was supposed to. I was wondering why my OG was so low then remembered while Iw as out to dinner with some folks. So when I got back at around 8:30pm I boiled it in a quart of water and added it to the wort, shook, and let her roll.

Sounds perfectly normal to me, but fermentation may not be 100% over at this point (although based on your hydrometer it probably is). I've had airlock activity die in as little as 24 hours. Take hydrometer readings on consecutive days - no change means your fermentation is complete.

To piggyback on that question:

If there is no change in SG from day to day, do I still need to have an airlock fitted on the fermenter? Or can I just toss a carboy cap on it and stow it somewhere for a few weeks before I bottle?

I think you can just keep the airlock on. No harm anyway if it is filled with water. Removing the airlock and adding the stopper may introduce bacteria into the wort/beer.

I'd just keep the airlock on personally. I've let beers age for months with an airlock and it does just fine.

Yeah. I was just trying to spread out my resources here. I have three fermenters and only two airlocks. Two batches finished fermenting and just sitting awhile. Now I want to make a third so I'd have to steal the airlock off of a current batch.

I'd recommend just using a blow off on your next batch. You could also bottle and let the beer age that way.

my most recent batch finished with visible/active fermentation within 12 hours of pitching. I used windsor yeast too. Most of my other batches w/windsor took 2 or 3 days to finish the visible/active ferment.