each monitor stores a specific number of versions in the change history. when in free plan and using local monitoring, you can view upto past 10 versions. paid plans offer more versions on change history.
if you need keep track of all possible versions, one potential option is to use email alerts to get the changes delivered to your inbox. you can keep any number of them in the inbox for as long as you need to. discord or slack webhooks can similarly be used to view them using those apps too.