No, a backup job that requires more than 16 hours to complete will not fail if the backup window is set to 16 hours and overtime is allowed.
I'm currently usign avamar version 19.7 to backup clients. However, when preparing for the policies and clients, I see there are settings: "backup window" and "overtime". I wonder, is there any conflict between backup window and overtime configuration ? if these are set to "16 hours" + "always allow overtime" respectively, will a backup job that requires more than 16 hrs to complete fail or not?  
backup window and overtime?