I moved this topic to the #General-Discussion forums since it has more to do with the entire franchise than just Age of Empires II.
The limit on forum posts has always been the case since the new forums were launched in June 2018. Forum topics which require regular updates over a long period of time are not well suited to these forums. Your forum topic can be converted to a wiki topic which can be edited by a regular forum user at trust level 3 or higher. More info on trust levels here and more info on wiki posts here.
As far as increasing the time limit on being able to edit forum topics for normal forum users, that is something that I can ask the team about but understand that the limit is there to discourage necro or spam edits. You’re welcome to send me edits to incorporate and after review I can update your original topic. You can also become a regular member on the forums and be granted the ability to edit your own wiki topics.