Chances are that neither the client nor the agency will ever know very much about what role the ad has played in sales or profits of the client, either short-term or long-term. ↗
There certainly have been a lot of changes, although they come in such gradations that most people have either forgotten, or, if they're too young, they never knew about them in the first place. ↗
I liked 35 and in both my novels that is the age of the lead characters. I tried making them my age but they just seemed to keep moaning about stuff. ↗
For me the writing, when I'm going to direct it myself, is really just the first draft, and I don't change it very much; I only change it on average about two lines per movie. ↗