I have been using a full cheek french link snaffle on Dancer for almost 2 years. I originally switched from an eggbutt to the full cheek for better control when turning (a previous trainer suggested this...her other suggestion was twisted wire which I ignored.)
I keep using the full cheek because we don't seem to have issues. I was reading today that bit keepers should always be used for full cheek snaffles. Is this true? My current instructor has never said anything and as far as I can tell we (Dancer and I) haven't had any issues.