Don't you think that actor is associated with his best role? And even if he plays some other roles, they can only spoil the perception of that best one, but won't change these associations. I think playing many roles is wrong. For example, can we imagine that Buddha and Jonathan Harker from Dracula could be so much similar in reality? But these roles are performed by one actor - Keanu Reeves. We abstract from his some exact role and share our impression among many roles.
So, my idea - which probably sounds absurd - is that 1 actor plays only one role in his life. Then this actor would be associated with this one role only, and not with dozens of that.