Im sorry about the loss of your dog, it can be really tough when you have a pet for so long
I have read so many articles online about Flemish Giants!
Generally, the life expectancy is 5-8 years (from what I have heard).
Its sorta like dogs - smaller breeds may live up to 18/20 years but a large dog may only live until s/he is 12-14 years.
Although - I do believe that neutered rabbits live longer.. so you may get a few more years from your bunny
ETA: lol, elrohwen! We must of been typing at the same time!