Change of status from H4 to H1-b

[Swathi1989]

Hi,

I am currently in H4 status and I have question regarding change of status from H4 to H1-b. I got my H1-b approved on November 08, 2016 and it is valid through July 30, 2019, I worked on H1-b for about six months and later changed my status to H4. Now I won't to get back to H1-b again, should I need to get a job before July 30, 2019 which is my H1-b valid through date to have my COS ? Or can I change my status to H1-b any time after my valid through period also (July 30, 2019). Can someone please help me in this?