How can you know, what you want, if you have not tried out a lot of different possible ways of playing the piece?
"get it in as little time as possible. "
Oh yes, people have so little time and there are so many pieces to learn... 
I mean - learn only one piece for a whole year, and you will get a totally different view on music!
"I learned this sonata in 2 weeks and that concerto in 3 days" - this sort of arrogance against music makes me really angry.
eh? If I have a tricky passage I want to solve the problem fast! Not go oh gosh, I have a lifetime, never mind! If I love a piece of music, I want to learn it.
Why even play a piece if you don't know what you want? It's a little pointless isn't it. Of course your opinion will change over years, experiences etc...but you have to know what you want at the present time! How can you ever expect an audience to listen to you if you play not knowing what you want to express?
In saying as little time as possible I mean being efficient with your time. If you deal with the problem instantly, and in the correct way, you will spend a lot less time on it than if you try futile methods on it. Most people practice 12 hours a day and gain nothing because they don't solve problems. They believe that the long hours will solve it.
Why do you call it arrogant to say I learnt a concerto in 3 days a sonata in week? It's not arrogant at all. If somebody learns a concerto in 3 days good for them, it shows they are passionate about the work (or have a deadline)...and also that they practice efficiently.
Learning fast also widens the repertoire. My aim in life is to play all the music I love...and I know that I will NEVER achieve that in 90 years or whatever..but I'll give it a damn good shot, and the only way to do this is to practice properly.