I just made a completely biased and unfounded claim in another thread and wanted to test its validity: I reckon that PCs on Linux do not get upgraded as often as those on windows. The reason most people upgrade so early on windows is because it gets slower over time until the point it becomes unusable, and most wouldn't even consider re-installing windows, so they just get a new one.
Maybe I can flesh this out for you, as based on my experience anyway. I probably have a different perspective than most on this board. There are two volunteer projects that I have been working on for the last several years. One is at a local high school and the other is at a nursing home.
With the help of interested students, I set-up a computer lab at the school that has 18 computers. Two groups of 8 Linux computers that are set up as two different independent networks, and 2 stand alone Windows computers. Students maintain, with my oversight, these networks and the Windows machines.
In the nursing home, we have 10 machines. 8 Linux and 2 Windows machines all independent, not networked. Though they do use a common Internet connection.
All these machines, all 28 of them with Windows pre-installed, were less than 2.5 years old when purchased. They were all bought at yard sales. Most were less than 2 years old, and were infested with malware. All were unusable due to software issues. I think a few had bad hard drives and a couple had bad power supplies, usually a result of over loading them with extra hard drives, CD/DVD drives, etc.
In short, my experience tends to support you hypothesis. People tend to replace their Windows computers when they get slow and infested. This is really illogical on the one hand. If the machine was sufficient to do the desired job when it was purchased, there is no reason why it couldn't be put back in that condition. On the other hand, if the price of a new, better computer is low enough, it could be that reconstituting the software would be a very significant percentage of the price of a new unit. So there are lots of ways to look at the purchasing decision when looking at the Windows world way of doing things.
As for my own computer purchasing, I have always built my own up until just recently. This past Christmas my daughters got me a new, custom made, JNCS, factory made desktop. My wife got me a ZaReason laptop. These are the only store bought computers I have ever had.
Even when I was still working, I built my own servers and client desktops for the office. I admit that I don't build much now though. My eyesight and hand-eye just isn't good enough anymore to make it enjoyable. Anything that has to be worked on I get one of the students to do it for me.
I know I took the long way around and got a bit wordy, but I think you are right emorrp1. I do believe that Windows users upgrade, for multiple reasons, more often than Linux users. This is probably one reason we aren't liked very much by computer manufactures and fix-it shops.