When Did That Happen?

Used to my golden, Lucy, was the first in and out of the water. She also dominated the window when we were taking a ride. Now, more often than not, Sable, my black lab mix, is in the forefront. She is the first in the water and the first one back with the ball. Heck, she used to wouldn't even attempt to swim. She would just stand at the waters edge watching Lucy. She also is in control of the window when in the truck now. Before she would make no attempt to put her nose out the window. Sometimes she lets Lucy up beside her and sometimes she won't budge. I don't know what brought on this shift in behavior? They are both 5 years old this year. However, Sable does out weigh Lucy by 20 pounds making it somewhat easier to push Lucy around in a tight spot. It's strange watching them change before my eyes. Much like watching one's children change I suppose. All I can do is scratch my head and wonder.