This adds an explanation, about which mirror is refreshed weekly and monthly. Since the [original forum post](https://forum.kaosx.us/d/2800-april-updates-and-some-news) is silent about which of both is weekly and which is monthly, I made a guess. The point is obviously, to prevent switching to that mirror for e.g performance related issues and finding the system in an old state and not knowing what is going on.