The lifespan of older (digital) camera's

Older cameras are often dismissed after a year or two, but they can still be astonishing. I shoot 35mm film with a Nikon FM and digital with a Nikon D200. I really love these two cameras but consider updating from time to time. Every other month i find myself gazing at the Olympus OMD EM-5 / Fujifilm X-T1 / Sony A7(s) etc. The Nikon D200 really is a great camera with all the controls that i need and want. The sensor however is from 2006, and starts to show it. ISO100 gives great 10MP pictures, but anything up to 800/1600 needs work to look good. Most of the time, i find myself more and more taking fast shots with my iPhone and use my (D)SLR for dedicated purposes. My photographs are urban or landscape during the day and nighttime shots (some long-exposure). The lifespan of the D200 amazes me, and I’m still happy with most of my shots. Do any of you guys own and use an older camera, and how do you look at the image quality compared to newer models? My main motto that great pictures can come from anything still counts, but being a bit of a nerd, I can’t help but wonder if updating will improve my photographs (ISO/size). What do you think about this and the lifespan of (older) digital cameras?