I don't change mine often. I get something I like and stick with it. Right now I have this layout as my cover photo. I didn't even adapt it to fit the space, just adjusted it so that the words fall into the area that shows.
I am picky about wanting a cover that looks good with my profile picture though. I don't like when they clash completely.
I love the graphic look but I really wanted to do something with my word of the year so I just used the layout as I had just scrapped it and felt like it was worthy of being used as my cover.