We go as long as we can. We don't upgrade to upgrade. The reason we got a new computer is because the other one kept revving. It was extremely loud. We had it fixed a couple of times but after awhile, you just have to break down & buy a new one. So for us, it's when it can't be fixed anymore! Same goes for our Printer.
I've had mine over 7 years. It's still going strong. The only downside to it is the processor being too outdated to run Windows 11. Other than that, brilliant laptop, performances really good, etc. Still looks like new to be honest. All I had to do is replace the battery.
I keep mine running as long as I can before upgrading. I had my previous one for 7 years before it gave out on me, I've had my current one for about a year at this point and plan to keep it for at least 10 if I can keep upgrading the components. Prior to the 7 year one, I had my one prior for over 10 years.
Whenever I can afford it I mean hardware can fail like anything else and when it does I have to respect that and have to get that hardware replaced. I build my own PC anyway. The good news is that one of my memory sticks had failed and since it has a lifetime warranty I had a replacement sent with no payment. Just this week I also replaced one of the 120mm RGB fans that are working but it's failing and they sent me two.
But at the end of the day when it comes to buying the full system at full price is not easy trying to get $3000 - My last PC that I had that I also built was around seven years
I upgrade when a new update comes out, I have to many in the house so I will upgrade one to make sure it's ok before doing the others.
As for hardware my old gaming rig is seven years old and since I don't game anymore I don't think I will ever spend anything on it now.
I'd say I upgrade roughly every ten years. I tend to upgrade to a couple of iterations below bleeding edge components so it costs me a lot but I think it's money well spent. My current PC is probably well over 10 years old now and cost the best part of £/$2,000 but it still runs everything I throw at it.
As it happens I'm starting to think in terms of a replacement because of an incompatible with Windows 11 (TPM). I've recently put together a list of desired components which totaled the best part of £/$3,500. I'm not sure I want to spend that much, graphics cards seem particularly overpriced right now, perhaps due to a shortage of chips? I might just hang on for a while.
I always go as long as I can with a PC or laptop. At the moment the laptop that I have right now which is nearly 9 years old is still running and the hard drive is the only thing that has died on me so far in it. I have replaced it with a smaller hard drive for now until I can get another 1TB hard drive for it and I have moved from Windows to Linux on it as well. The only other issue I have had with my laptop has been the charger has gone on me twice but I have been able to replace that with no issue whenever it's been needed.
My PC is now nearly 5 years old as well and even though it is still running, we have had issues with it and I have been unable to upgrade to the latest version of Windows on it and it will sometimes restart randomly which we believe is the PSU unfortunately. At the moment it is still running though so I am happy about that and hoping it will last a little bit longer.
I guess I can't really say yet. My current MacBook Air is now 10 years old, but it was the first new computer I ever bought. So I guess since I'm still using it all the time, 10+ years? 😛
Until I see severe signs of malfunction. I still have my Asus laptop I bought in 2014 for 400 bucks, yes I know the battery and its internal keyboard no longer work properly but it boots up just fine. I plan on replacing the aging HDD with a good SSD with SATA connector.
However, I wanted something more robust and with decent specs so in 2021 I bought a Lenovo laptop, with 20GB of RAM and a Ryzen CPU that surprisingly does not overheat when I do intensive tasks.
I mean hardware can fail like anything else and when it does I have to respect that and have to get that hardware replaced. I build my own PC anyway. The good news is that one of my memory sticks had failed and since it has a lifetime warranty I had a replacement sent with no payment. Just this week I also replaced one of the 120mm RGB fans that are working but it's failing and they sent me two. 
