Do dogs not care when they turn 8?

Meet Sierra. Sierra turned 8 in September and has decided she really doesn't care anymore. I am talking about barking at everything (unfortunately, my home has an abundance of windows). Also, in addition to the fishbowl set up, I am on a hill - so there is fishbowl backyard and wildlife. What does this mean? More barking!!! I am thinking my neighbors have got to love me at this point. Last, the new I-do-what-I-want doggie attitude includes sleeping on couches. When I catch her ... she just stares at me and has a "what are you going to do about it look?" Last, what is up with waking me up at 3 a.m. and wanting to play? Why do dogs not care when they turn 8?