The problem with that is that it’s not like professional players send us an email saying “we’ll be playing in an hour if you’d like to promote us”
more often than not it is the case that a fan happens to stumble upon the already active event and thinks “other people might like to know about this, I’ll see about getting a banner up for it”
Though, your idea of keeping a record of past announcements is an interesting one…
Also worth noting is the ongoing review of site notifications.