That can't be literally true, no release of Ubuntu is still getting updates after 18 years. At some point you have to upgrade to the next release, and that's not quite as simple.

The 'upgrade to next version of ubuntu' has gotten pretty good these days.

The only thing I would make sure to do is to have a separate home partition / volume so if you had to blow the underlying OS away after a botched upgrade, it's easily doable.

For the life of me I don't understand why having a separate area for your personal files isn't the default on every OS. Just pick a reasonable size for the OS part (20-30G?) and give the rest to /home

The laptop is 18 years old, Ubuntu was installed in 2017.