I second the last point.No, never. The clean install idea used to make sense back in the days of Windows XP. Nowadays it is not needed.
For me it would involve a huge amount of work doing all the software installs and doing all the configuration tweaks that I like. The last time I did a new install, I remember it took two days for one computer to get everything perfect. And I have five computers.
When Windows 10 gets its 6 monthly major update, that is very close to being a clean install. The registry still collects old stuff from programs that you install and uninstall where the developer didn't do a good job with the uninstall program. If you really want to you can run the free CCleaner to tidy that up. I do that once every few years as I don't really trust it and always have a system image backup just in case.
One thing you should be doing is the disk cleanup. Go to Explorer, right-click on your C: drive, click Properties. In the new window make sure you are on the General tab. Now click Disk Cleanup. Press Clean-up system files. Then tick all the little boxes (scroll to see them all) and then go ahead. This will also remove old versions of Windows which may still be there.
I have never seen any slow up at all since back when Windows 7 came out.
There is something very wrong if you are buying a new laptop every 4 years. Are you getting the cheapest low spec machines with old CPUs and not enough memory? Depending on what you use it for an i5 processor and 8GB will still deliver what most people need, and those have been around for a very long time. I wonder if your speed issue is really something quite different such as internet speed, or wifi speed. I went to help a neighbour who was planning to buy a new laptop and worked out that the real problem was his internet, so a new computer would have been a complete waste.
Hardware issues are probably down to buying from a poor manufacturer. Look for ones with good reliability. My old Acer laptop is 10 years old now, been all over the world, never any problem.
I ran Novabench on a first generation Thinkpad X1 and it achieved the same marks as a more recent HP Elitebook 745. The Thinkpad was at least 4 years older.
The X1 has an i5 8gb ram and 512gb SSD, the HP has an A10 pro, 16gb ram, 512gb SSD and they achieved the same score.
They both cost me less than £200 refurbished.
Both good enough for office work, both on the latest windows 10 and office 365.