Mark
Avoid iTunes, buy the hard copies
iTunes has been poor from the very beginning. It's always been a very poor app with poor features and prone to getting corrupted. Fixing those corrupted databases has been a major headache every few years. (If you use Windows computers, you have some alternatives for music management, but not so with Macs) The real rot seemed to start when they introduced the iTunes Match service, but Apple manage to consistently make iTunes worse with every new release. However, it is now clear that quite a lot of albums are being removed from iTunes (for whatever reason) and when that happens, if your database gets corrupted, you will not be able to download the music. You will not get a refund and you will not get access to what you purchased. Support staff (always cheerful but then with respect, it's not their money that has been wasted) will quickly refer you to the small print of the Terms & Conditions. So caveat emptor: buyer beware. Go back to buying the CDs or DVDs and rip them to a hard drive as needed. Decades later, you will still have access to what you purchased - unlike with Apple. In the meantime, write all your purchased albums (via playlists) to a CD. It's time-consuming and not ideal, but at least you still have the music.