adding my 2p: I'd expect a well-treated, mostly-left-alone Raspi to last a couple of decades, or at least ten years.
Other than that, in normal use, the deaths will be as such (in order of likelihood):
1. Accident. being stood on, something snapping off while being carried in a bag, whatever. (0 days to whenever)
2. Misadventure. A modding attempt gone wrong. (0 days to 3 months)
3. Not looking after it. This is slightly different to 'Accident', in that it happens slowly. This is like 'something snapping off while being carried in a bag', except you noticed it, and you could have made a case for it, but you couldn't be bothered.(6 mths - 2 yrs)
4. Wear and tear. You were nice to it, but sometimes, something's gotta give. HDMI ports can only take so many plugs and unplugs... and the same goes for SD slots, RCA jacks, and micro-usb power-leads... Luckily, this is a mechanical thing, and fixable... (1/2/3/5yrs, depending...)
5. Component failure. I have only experienced one case of 'component failure' in my life - the infamous mid/late 1990s motherboard capacitor problem. Nevertheless, those sorts of components go before chips do. (20+ years, depending...)
...anyway, there's my lopinions...
note: I may or may not know what I'm talking about...