Actually I think it is quite common for a writer to use and reuse certain phrases and images. This is especially true if you've written several fics. If you've come upon a particular turn of phrase that you like you tend to reuse it instinctively. This is probably most common in descriptions. After all there are only so many ways to describe the color brown.
I don't think it is a good or bad thing in and of itself but one does have to be careful not to use certain descriptive phrases over and over within the same fic.
Tank (who has always had a hard time coming up with different ways to describe a Lois haircut)
