@Samuel M. the problem is you are trying to extend timeframe in Monitoring Overview. There timeframe is max 72 hours because these are data prepared for fas load. If you want for example transaction flow for larger amount of data, or visits, you cen use Dynatrace Dashlets and than open them. In this way you will have access to any timaframe (according to your data retention). But be aware that collecting such huge amount of data on production may need huge amount of time or may crush DT client because of OutOfMemory error. You can always go to Settings -> Client and increase RAM there.