Karen, as long as your smoke remains thin and blue you don't have to worry about creosote. It is the big billowy clouds of smoke that you need to worry about.
Once the meat passes the 140 degree mark the checmical reaction of the smoke and the salts in the meat that creates the smoke ring stops but the meat will continue to take on the smoke flavor.
How did the smoke flavor of this brisket taste compaired to the first brisket that you did? If you think that it needs to have more smoke next time, repeat what you did in your first smoke. If you liked it just fine then just repeat what you did on the second brisket smoke. If you want it somewhere in between, continue to add wood but reduce the amount used. It's basically a big experiment until you get it where YOU like it.