Some things stand the test of time!

One of my favourite bands, pictured above, is AC/DC.  They have been together for almost 40 years and have sold millions of albums and sold out shows around the world.  They are unique in the sense that they continue to do one thing: Make loud, heavy, screaming rock music.  They did not experiment with some ballads, or try to soften their music, they continue to do what they do best, and we continue to buy the music and go to the shows.
They are living proof that when you find your niche and you love doing it and are great at it, keep going!  Now they have updated the way they present their music, the manner in which they market the product, but the product is still the same and they continue to be extremely successful because they know what they do stands the test of time.
In business it is easy to get caught up in trying to be the next big thing by going outside your area of expertise, outside your niche and sometimes this works.  However if you are successful at providing a service or product, and you really love doing it, be careful about ditching it to be the next big thing in something else. 
It's a fine line to walk between staying current and giving the people what they want.