Oooh, blankety blanks... I'm-a give it my level best - I hope you come back and tell me how close I am. 

how long should be the time for a person to open a case? (aready provided above, so no points for me) is it before 30 days for the expiry to open a(nything) ?

If this is about eBay's MBG (woo! acronyms 🙂 ) then it's 30 days after the latest ETA (!) in the eBay listing.