Piano And Keyboards

It depends on the piece. I play a lot of jazz, rock, funk, and adjacent styles, and so I'm typically going off of chord charts or just by ear, and in those instances, I can get something passable hacked together in a few minutes. If I'm playing an accompaniment part for a vocalist or soloist, those are usually simpler so as to not step on the toes of whoever is in the spotlight, so I can usually put that together in a week or two, with the caveat that that's not a big part of what I do on the reg. When I was doing a lot more classical type playing, particularly in college when I was getting my piano degree, I would do it pretty much the same way as you and it would take a similar amount of practice time for a relatively short but difficult piece, like a Gershwin prelude or a Joplin rag, or even longer for something like Danzon No. 2 by Marquez, which I did with my university orchestra, with the caveat that because I was spending multiple hours a day doing it, my overall turnaround time was quicker.