Hi @Luis Hernández!
I personally use different numbers of staves to sketch things out for orchestra depending on how far I am in refining my material, what my needs are or how big the orchestral forces I'm sketching out are going to be. If I'm sketching out for a string orchestra I usually don't need more than 3 staves (treble clef, alto clef and bass clef). If I'm expanding the string orchestra sketch for a bigger orchestra I use 6 - 8 staves: 3 staves for the strings, 2 for winds, 2 for brass, and 1 for percussion. Finally, if the score is really complex I will write things out for a full orchestra partiture upwards of 16 staves. But I rarely use just a 2 stave piano score for an orchestra - for me it's too small.
I've heard that John Williams uses 8 staves when he sketches out his film scores.
Great topic!