I'm also an IT professional and, like you, have many plates to keep spinning. For me, the distinction in this area is what would go on your job description. Would it say, in a list of things for you to do, "Maintain backups"? Yes, quite likely. Would is say "Maintain tape stock"? Probably not. The difference is one of specificity. You are responsible for maintaining server backups. Part of that is, obviously seeing that you have an ample supply of tapes. So, "Maintain backups" could be an area of focus/responsibility, but "maintain tape stock" wouldn't. So, what do you do with the tape stock issue. It's still a problem. This can be addressed in a couple of different ways. I think the best way would be as an item in a tickler file or as an item on a checklist that goes in a tickler file. Let's say, there are several things you need to do/check on quarterly. These things become projects. You could list them on a piece of paper and put them in a tickler file with a note on it to tickle for every three months. Then, when you come to the day on which it sits, add the items on that checklist into your Projects list and have at them. In the case of "maintain backup tape stock," you may see that item and not add it because you've got plenty of tapes to get you through the next three months or you may not and choose to make it a project to complete.
Overall, the difference between a project and an area of focus is one of outcome. Does "Maintain tape stock" have an outcome? Yes. Periodically, it becomes a project to address with the outcome of "Have plenty of tapes for the next x months." On the other hand, "Maintain backups," in my mind, does not have a specific outcome. Now, could you argue that it does? Yes, you could say it's a project to be done every day where the outcome is to "All servers were confirmed to be backed up successfully last night." For me, it comes down to the illustration of a job description--what areas of responsibility would be delineated on it today?