I've only been riding in my adult life for 1 1/2 years now. So I'm still on the same bike, but I have added side bars, new seat, new tires, gone through two computers, two helmets, two bike racks, and a plethora of other miscallaneous items (tools, bags, clothes, etc...). Probably spent about twice as much as I did on the bike on miscallaneous accessories since.
Now I'm thinking of going for a road bike.