I have a Nikon D80 which I keep my Sigma 50-500 and a D7100 I keep my Nikon 18-200 . This gives me a super zoom to 500mm but also a wider angle at 18mm . This set up is perfect for air shows any wild life areas . I can put the 500 on a tripod and still have a lens for shooting handheld.
Ive also pondered with the idea about doing this. Thanks
I sold my Mikon 18-200 and bought the Tamron 18-400 as a kind of walk around on vacation lens. Had it about six months now. Very happy with the new lens.