Like others have said, it really depends on the style.

Recently I've been making a lot of tech and minimal house, and repetition is key to give it a steady, "rolling" groove. This is even more important when performing live, especially in a clubby environment. When performing, a good trick is to have a distinct pattern which you can revert to at anytime. If you're feeling adventurous, switch it up! But keep your tempo steady so that you can go back to same groove whenever you want.

As for producing, another trick I like is to make slight variations rather than adding whole new elements. An extra hi hat beat in a pattern can keep a groove remarkably fresh, even if you did not change much.