You'll need a backup plan if you've been hanging on to Aperture years after its retirement. Apple has warned that its pro photo editing tool won't run in versions of macOS released after Mojave (that is, the upcoming 2019 release and beyond). If you want to access your Aperture libraries beyond that, you'll have to migrate them to either Photos or Adobe's Lightroom Classic. This isn't a total shock when Apple hasn't updated the software for five years (and hasn't even offered downloads in four years), but it could prove a headache if you've been deeply attached to Aperture's methods.