My principle in purchasing electronics is to buy what you need and skip two or three generations. For sensors I went from 300D to 5D3. My next purchase of the body is going to be several years down the road. Unless I inherit a million dollars (US or AUS) - fat chance of that happening!
In other electronics, me too. I still have, and regularly use, a Sony XBR TV I bought in 1985 or 86. I've only just retired a Sony SLV-R5UC S-VHS VCR after 20+ years of use. It still works but I no longer feel compelled to record anything with it and I have a different deck for playback.
I'll keep some of my cameras like that too, i suspect my 40D will be buried with me; I'm rather fond of it. Or maybe I'll take the Konica, it doesn't need batteries.
Other cameras and lenses will come and go, as suites my needs, since the technology is making for very compelling improvements quite often. In other areas, I buy the best i can afford and take care of it and it generally serves me well for a very long time.
I think I'm actually reaching that point with camera gear too. I'm still on the lookout for something that fills a niche i might want to work in, but overall, the gear I have now is at a point where I could do almost everything i'd want to do with it and not suffer any serious compromises or work-arounds like I had to just a year or 2 ago.
I've noticed this when I go on a road trip lately. I no longer have a trunk full of gear, each bag containing something best suited to a narrow range that optimized its performance. I'm down to a much smaller, more manageable pack size and I'm not left facing compromises as often.
The only remaining niche I'd like to refill is a good, fast camera, like the 7D (but better), for working with longer FL lenses.
The 60D can work with my 100-400mm lens well enough for still shots but I'd like a better AF system for moving subjects, like the 7D's or better, with good hi ISO performance, like the 60D or 7D or better, but also with better low ISO, like the 6D at least, or preferably one of the competitor's cameras. And I don't want to spend more than $2k for that ability. When I do, I expect it may also replace some gear I'm using now, so I can improve hardware capabilities while also reducing the inventory I carry.
So that's my hope, a 7D2 or 70D that I can afford and that will also fill the speed AF and low light niche yet still provide better low ISO performance too. Since I'm in no rush, I can wait to see what Canon, or others, offer later this year.