I set this too high in a previous project and it caused my project to fail.
I have no idea without knowing the specs of your machine. Could you explain why the project failed? An image would help.
What was the burn speed? Where did you set the white space traverse speed?
Just test. The manufacturers defaults are also not correct, in most cases. Test what’s best for your specific project. The maximum speed will be the maximum speed your laser can travel, refer to the specifications.