If they gave more time than just a few months, in example at least an entire year, then people could at least download those files before hand. Not sure how long this would take and how stressful this would be for their servers.
Is anyone actually surprised by this? How can you think Twitch is a longterm archive? Its like having backups on Microsoft or Adobe servers. Do not trust them and always have a backup plan! Not even YouTube is, because they deleted old unused accounts and therefore the associated videos. Not sure how far this gone though. I wouldn't be surprised if Amazon/Twitch announces some premium service where all files will stay active if you pay a monthly fee.