...and this is why I keep older versions around - I stuff each install package into the b/u drive as I download them. You never know when you need to reinstall the Last Known Good.
I'm gonna hold off on upgrading DS until I get my new drive installed and everything transferred to it (I ordered a 4TB NVMe SSD drive that just arrived yesterday - I'll be replacing my 2TB drive with it - just waiting for the ext. drive enclosure to show up before I start.)
But, yes, my main toys' install files are always backed-up, no question.