Kodak Bullet by
Narsuitus, on Flickr
I tend to keep my cameras until they need to be replaced. In fact, I still have the first camera I every used -- a Kodak Bullet.
Over the decades, I have sold and/or replaced the following:
Brownie (3) (sold after purchase of first 35mm SLR)
Diana (sold after purchase of first 35mm SLR; it latter became a popular cult camera)
Graflex 4X5 view camera with 135mm lens (sold to raise money)
Kodak Instamatic 104 (sold after purchase of first 35mm SLR)
Mamiya Universal 6X7 with lens (two) (replaced by medium format rangefinder)
Mamiya-Sekor C2 TLR camera body (replaced by medium format rangefinder)
Mamiya-Sekor C22 TLR camera body (replaced by medium format rangefinder)
Mamiya-Sekor C220 TLR camera body (replaced by medium format rangefinder)
Miranda Sensorex 35mm SLR body (broke too many times)
Nikon EM, Black 35mm Body (replaced my disposable backup body with Nikon N70)
Nikon F Black 35mm Body (replaced by F2)
Nikon F Chrome 35mm Body (replaced by F2)
Nikon F2 Chrome 35mm Body (replaced worn body with new F2)
Nikon F2T Black Titanium 35mm Body (sold two for profit to collector)
Nikon F3 35mm Body (replaced with Nikon F4)
Pentax Spotmatic (sold 1 of 4 to raise money)
Polaroid Portrait Big Shot (sold after Polaroid went bankrupt)
Polaroid Square Shooter (sold after Polaroid went bankrupt)
Polaroid Square Shooter 2 (sold after Polaroid went bankrupt)