I learned to keep them very short in my piano days, you don't want any click-clack on the keys.
I was stunned to see Geddy playing with his fingers in the several films they released in their later years:. I'd wrongly assumed he was a pick player to have that tone.
Then I remembered reading about an in-house experiment that Bob Taylor staged. In an effort to find this or that tone, he made several of his standard models in several prototypes using varied wood combinations.
While this did indeed show him what combinations worked for a certain tone, there was one factor that could not be engineered for: A given fingerstyle player's hands.
Some guys had more fat, some were bonier, it was all over the place. He described this X-factor as 'Bone Tone', over which he had no control.
So . . . if I had to woodshed some Rush, me, I'd be forced to use a pick to approximate that tone.
Geddy doesn't. Who knew?