Windows need a regular reinstall. Not so much on linux.
My daily driver at work is the same install from 2000. I was so impressed with debians abillity to do a major upgrade, that it kind of became a game, to see how long i could upgrade it. A fresh install and copy over /home would have been more sane ;)
Also with lvm you can migrate your running install to a new os drive while working. So hardware swap is a 5 min process. Boot new hw on old disk, with usb adapter. pvmove the install to the new drive. Install grub.
I do fresh installs on many other machines tho. My daily driver at home and the emergency laptop is installed when they are aquired, and upgraded as long as the hardware functions.
Really? I must not have much to say ;)
Read the debian release docs about the major upgrade when that time comes. They sometime contain important adaptations to make your upgraded install similar to a fresh one.