Cat hit the nail on the head. We're not in charge of this, the yeast are. We can't really arbitrarily decide when something is ready, or how long something takes.
Where fermentation is concerned, If you arbitrarily move your beer, like to follow the silly 1-2-3 rule, you will often interrupt fermentation. Because sometimes the yeast won't even begin to ferment your beer until 72 hours after yeast pitch, so if you rush the beer off the yeast on day 7 then you are only allowing the yeast a few days to work.
Besides, fermenting the beer is just a part of what the yeast do. If you leave the beer alone, they will go back and clean up the byproducts of fermentation that often lead to off flavors. That's why many brewers skip secondary and leave our beers alone in primary for a month. It leaves plenty of time for the yeast to ferment, clean up after themselves and then fall out, leveing our beers crystal clear, with a tight yeast cake.
That is why more and more folks are skipping a secondary and leaving the beer in primary for a month, or if we do opt to use a secondary, then to leave the beer alone til fermentation is complete, and even a few days longer (I usually wait til day 14 if I am secondarying).
Now in terms of carbing/conditioning in bottles...that is another process that really we don't control. The 3 weeks at 70 degrees
, that that we recommend is the minimum
time it takes for average gravity beers to carbonate and condition. Higher grav beers take longer.
Stouts and porters have taken me between 6 and 8 weeks to carb up..I have a 1.090 Belgian strong that took three months to carb up.
And may still need weeks to lose the green-ness. The Belgian took iirc another 3-4 months to begin to taste great.
Temp and gravity are the two factors that contribute to the time it takes for this process to happen. But if a beer's not ready yet, or seems low carbed, and you added the right amount of sugar to it, then it's not stalled, it's just not time yet.
And even if you long primaried or secondared, that's not going to affect how long it is going to take the yeast to carb the beer. It MAY affect condtioning process (I've never noticed either way, except to say that my beer is much better when I primary for a month and then my beer bottle conditions for as long as it needs to condition.) But the yeast is still going to need however long it is going to need to make enough co2 to carb up the beer.
Everything you need to know about carbing and conditioning, can be found here Of Patience and Bottle Conditioning.
With emphasis on the word, "patience."
All in all my "normal" beers are 8 weeks from grain to glass usually. 4 weeks in primary (or 2-2 secondary) and then after 3 weeks in the bottle, though they may seem carbed, tend to take another week to come into their own flavor-wise.
But it's not an arbitrary process, and it is not really something we can control.
It may seem a long time, but it is wirth it.