My Windows PC is also well over 10 years old: started life on Windows 7 but upgraded it to 10 when that came in. It still works and has loads of hard disk space left, though it can be a bit slow at times.
I also have an ancient Mac which is fairly full, largely because I have most of my music and photos/videos on it (which is also why my PC is not so full). It won’t let me update from its current operating system (El Capitan, Ithink), so there are certain things I can’t run on it. And I do have an iCloud subscription to hopefully keep it all backed up, and an iPad and iPhone.
So…..thinking I should get a new one or the other, but not sure which. I haven’t totally joined the brigade of Mac-lovers, and certainly feel more at home on Windows, despite all its foibles.