The obvious benefit is reduced repetition, and the less obvious one is that these pages are found in search by people who are not yet customers. Somebody searching for how something works, what it costs, or what to do about a specific problem lands on your answer, which is both useful to them and the strongest possible demonstration that you know the subject. A knowledge base is content marketing that happened to be written for support reasons.
Build it from what has actually been asked rather than from what you think people should know. Go through your last few months of emails and messages, list the questions, count the repeats, and write the top ten. Written in the customer's words rather than your industry's, because that is both how they will search and how they will understand the answer.
Keep each page to one question. A single long page covering everything is difficult to search, difficult to link to, and difficult to keep current, and it cannot be surfaced individually. One question per page means you can send somebody a specific link, which is the thing that actually saves the time.
Write answers that are complete rather than partial. A support page ending with an instruction to contact you for more detail has not resolved anything, and the visitor now has to make contact anyway with the additional irritation of having read something that did not help. If the honest answer is that it depends, say what it depends on.
Then keep it current, because an outdated support page is worse than none. Anything mentioning prices, timeframes, or how a process works needs reviewing when those change, and the simplest discipline is to check it whenever you notice yourself giving an answer that differs from what is published.
Link to the relevant page when you answer somebody directly rather than retyping the answer. This does two things at once: it saves you the typing, and it teaches customers that the material exists, which is what eventually reduces the questions. A knowledge base nobody knows about produces no reduction in support at all, and the most reliable way to publicise it is using it yourself in ordinary conversation.