Favourite pin = MM
Arrival of 1st MM we owned: 1998
Departure of 1st MM: 2002
Length of ownership: 4 years
Arrival of 2nd MM (see picture below): 2007
Departure date of 2nd MM: never
Length of ownership: currently 5 years
So looks like the total is 9 years (and still lovin' it).
I must say though our new pimped out Tron Pro 2D is an amazing pin as well, been here 58 days at this point and I can see it putting it MM ownership type time at our place!