Personally 5-6 years but I also hold on to cameras for that length of time. If the camera, computer and editing software are all about the same age they'll get along well for as long as you use them.

I don't trust mechanical HDDs after about 5 years of continuous use and will back them up to a newer drive.

For me, there is no specific time frame, it varies..... So it's just up to the point where it can no longer handle or keep up with the newest development in technology and media creation.

I have to go with @Steve_Rhoden 's reasoning in that my previous computer was from 2014. It was only with Vegas Pro 18's AI FX (which didn't work in the old i7-4770) that it became clear that it was time to modernise - which I did in 2020 ✔️✔️✔️

It depends on what hardware advancements have been made since the last build. I recently "re-built" my system due to the introduction of Alder Lake. I moved from 4770K to 12700K, SATA EVO 860 SSD to WD Black SN850 NVMe, the difference is VERY noticeable.

On the other hand if you have been running a high core count Zen 3 rig with an SSD I don't think there would be a reason to upgrade at this point in time.

Then again I'm very particular about the parts in my PC's, the noise, thermals, etc. so I build my own systems. I've been using the same case for 20 years, same Seasonic power supply for 15 years, etc... I only replace the parts that need replacing.

I believe the survey is for business systems, so with that aspect I think that 3 years is sufficient to regard them as obsolete for tax and one can get new ones.

As for personal hobbiest, if it ain't broken and run's relatively OK , keep.

You should upgrade your PC when you are certain you will have no production deadlines looming for at least six months. That will give you a "safe zone" in which to work out the kinks, bugs, and become familiar with your new system's capabilities and limitations.

For myself, 3-4 years. And as @Steve_Rhoden depending on the media I would be editing. Right now, 4K is all I need. So my current computer that I built is fine for what I do. I have room to upgrade the RAM (still 2 open slots), CPU will take a Ryzen 5000 series, I still have PCIe 4 in both NVME slots along with GPU.

My only holdout is the graphics card. When the AMD RX5000 series came out, I said I would wait for prices to drop. Bad bad move on my part.

All in all, my current computer build will be with me for a while to come....

If you have money to burn, do it on a schedule.

Otherwise do it when the hardware, software and process you use would be made more efficient by changing hardware.