Oracle Certified Professional: Java SE 11 vs Java SE 8

I want to ask the community about their advice for preparing the OCP for java 11 exam, how mutch time needed, the recommanded materials and is it valable for JEE developers with 3 to 5 years of working experience ?

I want also to ask why the Java SE 11 Developer (1Z0-819) exam is an OCP exam and have no OCA certification required ?

The exam duration is 90 minutes as opposite to OCP 8 which is 150 min and requires OCA certification which duriation is also 150 min. It seems java 8 exam have reacher content ?

So do you recommend passing java 8 certification over java 11 certification ?

Do you value certifications in general for developers ?