Current main computer of the household is five months old, and it set us back about two grand in parts at the end of the day. Core i7 7700K, Z270 board, 32GB of RAM, Samsung 960 Pro SSD boot drive, etc. Only kept the monitor (two year old 4K 24" Dell) and video card (GTX 750) from the machine it replaced. All housed in an ncase M1 mini ITX case. It's kind of a beast. My girlfriend is a professional photographer, and this thing serves her well. Literally the fastest Photoshop machine money can buy. Way faster than her old machine (2011 era Sandy Bridge system with a few upgrades along the way) for her work. An outrageous computer like this is a very bad deal for anyone not fully utilizing it.
My laptop is a work-issued (and used for both work and personal stuff) Dell Latitude E5530. Five years old and still doing pretty OK. I had to upgrade it to Windows 10 and I don't think this laptop likes it. It'll be fine for at least another two years.
GF's laptop is a Dell XPS 15 bought last year from the Dell Outlet. Skylake i7 quad-core, 16GB RAM, 4K display, SSD, etc. Was $1099 refurbed on the outlet when that build new would have been fucking $1849. Does 70% of what her desktop does, but on the road for when she's traveling for work (and almost never even opened at home). This replaced an old Thinkpad T510 (i7 Westmere) that was still a fine machine, but garbage for photo editing (and she's been traveling more for work).
So that's 0-1, 5-7, and 0-1. But if you asked me this time last year, it would have been 5-7, 3-5, and 5-7.
No tablets or other tablet-like bullshittery in our house. We do both have smartphones, about a year old.
That all being said:
For 90% of what 90% of people want to do on a computer, the $300 desktop Walmart special that you bought in 2009 (I'll draw the line at Windows 7) probably still does the job and is chugging along happily, as long as the OS is cleaned out every once in a while, and you don't fill it up with garbage.
And laptops being barfed on or hit with sledgehammers aside, computers essentially don't ever wear out. You might have a hard drive or a power supply fail during a computer's usable lifespan, but the main guts of a computer will last essentially forever, long past their usefulness.