I have sfdc org which is showing 55 days remaining message on top. generally if we have enterprise trial org it expired in 30 days and if we have developer org it never expires until it is not used for specified time. Also i am not able to see system overview option in the left search option. Check the screenshot and it would be great if you can guide me on this.
Actually Partner enterprise edition get different expire time.Probably around 1-3(My results show 1 year.Not sure what is exact but it is more than 30 days atleast) years expiration time.So the thing to check here is that if this org is generated from environment hub as an partner enterprise edition.
To check this you can go in setup->company information
See this link for more information.
I just spun partner enterprise edition org.I'm not sure how to find the expiration date actually but under company information section for all licenses i'm seeing a date one year later from today for expiration.So i think this is it.