Random Poll of the...I don't know...a really long time ago..

[Kor]

Basically, when you're awake, when do stop being able to function in your 100%?

I'd say with me it's about 10 hours.

[GinRei]

100%?  That'd be about... 7 hours.  Now, if I were to say 85% or so (which is where I'd say the difference between 100% and "not 100%" truly starts showing), I can go for pretty much 14-16 hours easily.

Also, I read somewhere that your... "awakeness" depends on the previous night's sleep, not that night's.  So how well rested you are on Monday is based on how much sleep you got Saturday night (going into Sunday morning).  Obviously there are extremes that change this, like 12 hours Saturday and then 2 on Sunday, but I think the general gist is supposed to be "full night" Saturday vs "enough" Sunday.

[Vylash]

After 20 hours

[Raifuujin]

Well, about 15 hours is when I know, I should be sleeping, because my head is already gone. If I push past it....I can go for awhile, but it wouldn't be the best idea :x

[GinRei]

After 20 hours

I call BS.  It doesn't count if you have to juice up with coffee, soda, or energy drinks.  100% isn't the same as "How long can you stay awake". 

[Kleene Onigiri]

Voted 12h.
Also depends what you do in those 12h XD
When I study, I'm sleepy after 3h

[Akonyl]

if I wasn't doing much the entire day, then asked to exert 100%, I'd say around 15 hours. I don't really get gradually sleepy usually, it just hits me all at once.

now, if I was asked to work at 100% the entire day instead of just being able to be at 100%, it'd be a different story

[miyano_shiho]

Maybe around 12 hours for 100%, but I could still stay up for another three hours, I think.

[KangarooGirl]

It really depends on what I'm doing though. If I'm really busy at work I start feeling the strain at about 4pm which puts it at 9 hours. But if it's only a moderate day I can last close to my whole waking time which is almost 16 hours.

[kkslider5552000]

20, and even that's arguable.

Of course for me the " a good night sleep" is where the actual challenge is.

[Vylash]

After 20 hours

I call BS.  It doesn't count if you have to juice up with coffee, soda, or energy drinks.  100% isn't the same as "How long can you stay awake". 

With the exception of a glass of orange juice every morning, it's just water for me

[aly_angelflight]

17 hours, though really, time of the day has more of an effect on my alertnes... ^^;

[Kaito Lady]

long really long, but it basically depends on what mood I am and on what I am doing..but generally speaking...
....more than 10 hours....far more than 10...

[Jecka]

15 hours. When 10 pm comes around, I can just fall asleep
of course I can probably make it to 16 hours, but that's usually uncommon :X

[Memesu]

About 17 hours.