Speaking as a Grade 1 instructor with 5000 hrs dual given (at least I used to be until a forced career change). I have supervised hundreds of instructors over the last 20 years. Some of the very best I have worked with were actually very junior Grade3's. Some of the worst I have worked with were Grade 1's who thought they knew everything. Key word is attitude. I'll take a bunch of grade 3's with the right attitude over a know it all any day of the week.