When I find new worthwhile information. A and B work. Keeping content fresh matters more than many realize. While an About page seldom requires change, most containing content need to be updated or modified frequently. And new pages need to be added as possible.
Fresh content encourages people to return to see what is new.
Once a month is not often enough for most sites. While worthwhile content is a must, it's best to find some at least every two weeks, even if this means you work overtime. I fix what I find. This question was asked in a tricky way. But the fact is, it is very difficult to put up a page that does not contain an error or two.