It is obvious that websites need continuous improvement. Just browse around for a few minutes and discover the sites that are looking old and obsolete. But there are many other reasons to redesign your site. Some of them are not obvious but are at the core of the site.
All websites should be in a process of being redesigned or renovated.
Will you select a team with the right mix of experience and talent? From the looks of the websites of many of the companies offering their design and development services it appears that many are one person operations. Either they are tech-gurus and lack the aesthetic abilities or they are artistic types that lack the technical know how to build a complex site. Building or redesign a website is best done with a team. A team can synergize their abilities and create a much better site. Your website is your signature. It is often the only way for people to evaluate who you are.
Your profits depend on the quality of your site.