Read the book twice and saw the film multiple times ....
I didn't think the starlet (Sue Lyon, I believe) was too old. Starting with the killing of Peter Sellers at the beginning of the movie was a stroke of genius. Thoroughly enjoyed both the book and the movie. Nabokov wrote the sceenplay with help (uncredited) from Kubrick. Fortunately, as in most of her screen roles, Shelley Winters was killed off early. She lasted so long in A Place in the Sun (American Tragedy) that people in the audience were prompting Montgomery Cliff to hit her with an oar.
I didn't think the movie was overly long. The dramatization of Dickens' Bleak House was six hours, which I thought was just about right.