A game with the subtitle "create history" does, of course, need means to let you do just that. It is important, however, to see the difference between events and their interpretation.
The game creates history journals for dominios, asentamientos, personajes, batallas and even individual soldados. The later are the only journals that will ever get lost or deleted - when a mortal soldier is buried, his history goes away.
All other journals are for eternity. You can always find out when a realm was founded and what happened to it when, however that information may need some research to obtain. But the game keeps this information on everything, forever.
Some events are public knowledge and everyone accessing a realm, settlement or character details page will see them. Many other events, however, are private. Only the player of a character, owner and visitors of a settlement or members of a realm will see those. Your access to events on the realm and settlement level can change over time, but your access to information will not - if you were owner of Keplerville for two years, everything that happened in that time will always remain visible to you. The same is true if you visited a settlement for some period of time.
The journals are also used as the event and notification system of the game. If your character gets attacked, you will get an event in your character event log, for example.
Some of these events generate temporary journal entries, that will disappear after some time because they are not of historic significance. The warning that you are being engaged will disappear, but the battle you fought will not.
Finally, some events are more important than others, and to make large journals easier to read, you can filter out the less important events.