There was a 100% positive vote for me to eat the three-years expired gum so here goes. I will write as I go. I have decided to eat two pieces at once as it is the "pellet" style rather than sticks of gum.
SMELL: it smells pleasantly minty with a "mountain frost" edge.
CONSISTENCY: slightly tackier than new gum, not smooth and shiny, probably due to the fusty air in my cupboard.
TASTE: now i don't think they made this mountain frost flavour for very long because it is suspiciously chemical. I am nervous about swallowing the resultant mouthful of saliva but I will force it down!
TASTE UPDATE: within a minute almost all flavour has completely vanished! The half life of flavour must be very short! I am chewing a mouthful of tasteless petrochemicals.
THE VERDICT: I feel a bit funny. I have gone blind in one eye and there is a ringing in my ear. Please someone call an ambul