Recently I watched Kirk Whalum's Gospel According To Jazz Chapter III and I discovered that the are some things you wont ever do at anytime if you dont play in every key, And since that day I started to do everything in every key.
The bounderies that we always had; getting bored, feeling that we' not progressing even if we' ve got so much material from around here has always been caused by the limits of thinking in one or few keys, so if you're just starting out, never make the favourite key mistake but develop the 'every key habit'
This hs been amazingly helpful me
God bless you everyone.