When your marketing communications create a single impression for your business, they build a strong brand. Stay consistent in your marketing by
Projecting a consistent look.
Projecting a consistent tone in your communications.
Projecting a consistent level of quality, demonstrated by consistent communications, consistent products, and consistent services.
Stick with your brand. Don't try to change your brand image unless you're certain that it's no longer appropriate for the market. (And if that's the case, you better be prepared to change your business — because your brand is the public representation of your business.)
Imagine how tired the people at Campbell's Soup must be of their label, but imagine what would happen to their sales if they abandoned it simply because a fickle marketing manager said, "Let's try something new.