Upload & Sell: On
There is no "normal" rebranding. Companies rebrand -- individual products, product lines, divisions, or the whole business -- because they have identified specific changes they believe they should make and which justify the costs associated with rebranding.
You might change the name of the company if, for example, you believe it is a weak trademark, or you conclude your current name or branding collateral are not suitable for your target market, or your brand has been damaged in some way and you believe a fresh start is the only way to rebuild goodwill.
A trademark might be weak if it is merely descriptive of the goods or services, or is otherwise not strongly distinctive. Companies that change the entire company name sometimes do so to increase distinctiveness. Small businesses often start off with heavily descriptive wording as the brand in order to communicate to potential clients what the brand stands for, and later decide distinctiveness is more important.
Take me, for example. "Ian Ivey Photography" is partly descriptive. The word "photography" is a generic term for what I do. "Ian Ivey," my name, is distinctive in its combination -- there aren't that many people with my first and last name combination in the world -- but the use of the primary photographer's first and last name, plus the word "photography," is about as common as lies at a political convention.
Consequently, my business name is really only as distinctive as my name is memorable. At some point, probably soon, I'll remove the word "photography" from my branding, because including it actually diminishes the distinctiveness of my brand.
So, that's one reason to rebrand: to increase a mark's distinctiveness.
I'm also in the process of rebranding because my original logo is lame. It looks cheesy and fails to convey the sophistication I wish to communicate based on my current approach. I don't need to change my name to achieve that goal. However, I do believe removing the descriptive matter from my mark is likely to improve my brand image marginally: I believe it looks stronger, or more confident, to leave off descriptive matter.
So, as others have asked, what are your goals? What about your current brand are you dissatisfied with?