When we make significant changes to elements that affect certain critical aspects of our site (a very limited number of specific places, like user registration)

When we make significant changes to elements that affect certain critical aspects of our site (a very limited number of specific places, like user registration) we sometimes walk through manually just so we can sleep a bit easier. To date, our test coverage has been sound and we haven't caught anything this way. It may be redundant but we like to see it for ourselves just to be sure.