You're right with regard to later OS' not showing as purchases. However, you just need to keep a backup copy of the installer. So, just make sure to download Mojave from the appropriate page on the appstore, before Catalina is released, and you should be good to go. Failing that, I'm pretty sure Apple does have the installers linked elsewhere.maschinelf wrote: ↑Sun Sep 15, 2019 8:45 am Thanks, yea I'm pretty certain I downloaded it. Though I think OSes stopped showing as app store purchases after Mavericks. I know it used to work before that you could register an os as a purchase and then download and install it later, sometimeseven after the next os became available, but something apparently changed after Mavericks. I could be wrong about this though. I also have another Mac running Mojave which is with me, so I'll check later to see if Mojave shows as a purchase.
And yes, you absolutely can install it after the next OS drops. The only limitation on OS installation seems to be the inability to downgrade to an OS that is dated earlier than the one currently installed. To safeguard against any issues, clone your current drive before installing Mojave. You could even make a fresh install with the current OS, and clone that. I use SuperDuper for my cloning. It's free, and hasn't let me down in the many years i've been using it.