As a musician, you generally want to cover every facet of the sonic spectrum that you can. Every artist from Lady Gaga to Radiohead have made it a lifelong pursuit to chase their muse wherever it will guide them. Then again, if it ain't broke, is there any real reason to fix it?
Yeah, while it's admirable to take control of your sound, other artists have made a career out of delivering the same types of songs time after time after time. Before you start sharpening your pitchforks, not changing your sound is not necessarily a bad idea...if it is done properly. In fact, some bands on this list have gotten their sound down to a science to such an extent that they can pretty much do no wrong, but it's anyone's guess as to where your band will fall.
Oftentimes, a group will find a sound that makes them millions, and then proceed to copy themselves to the point where every single song sounds tired. Then again, if you're a fan of any of these artists, you pretty much know what you're gonna get before you've even heard a note of their music. They may have cut some fat here and there, but this is the best (and worst) of the artists who played it safe.