Redesigning a website can easily be done especially if you don't have anything to do at all. But come to think of it, the consequences of your action may affect your website in a drastic manner. It can go down the search engine rankings or it can also affect your conversion because it can also be possible that the original design of your site is more user-friendly than the new one.
Here are a couple of valid reasons why you should redesign you website.

To address communication and transfer information

Are you considering changing your website from being a plain brochure to ordering on-line? If so, then it is a valid reason to redesign your site. It would be beneficial for the customers and the organization itself. It would be more convenient to the customers and it would be a faster transaction for a lower cost.

Sales are going down

If the sales are going down there must be really something wrong. Although there are also some other factors other than your website that must be considered; like if there are changes on the pricing, kinds of products and services your organization is offering. But if your conversion is not sufficient then this might be the best time to redesign your site.

Aligning with corporate strategy

There might be also a need to redesign your site if there is an improvement in your corporate strategy. This is to have consistency to the reformation towards betterment.

To give customers more value

In every business, customer is always the priority. The reason is because customers pay the bills and pay the salaries, in other words, they keep the business running. Point given, it is just right not to give them a hard time during a transaction. So, if you noticed that a customer usually takes a lot of time just to finish her on-line transaction then maybe it is time to redesign and make your website more convenient for them.

To sum it all up, redesigning is done for valid reasons though the decision is still on the site owner's hand. For your effort not to go down the drain, don't redesign your website just for the heck of it. Do not just do it because you have the money and especially not because your competitor redesigned their website.