Early beta/alpha builds of Scrivener had a timer-based option in the automatic backup pane; an option that was removed during testing because it is effectively useless. The problem is that every fifteen minutes or whatever, you’ll be madly typing and doing stuff—and suddenly the software cuts you off with a modal progress bar while the project backs up.
Now if you have one smaller project and a very fast drive, this won’t be a massive inconvenience, just an annoyance as you pick up your writing stride again (which is not to be underestimated, this kind of stuff gets under your skin quickly). But think about this problem on a larger scale. What if you have two projects open? Will they each have their own fifteen minute timer? If so does that mean you’ll be typing merrily along in one project, and suddenly some minimised project in the background triggers a backup—forcing you to wait until its done? What if you have five or six projects open? Will you be stuck staring at a progress bar for 10, 20, even whole minutes at time for large projects, “randomly” and as often as every five minutes, throughout the day?
All right you might say, have it be a hard clock with all eligible open projects are backed up simultaneously. That’s pretty awful as well! Again what if you have five projects open, each of which takes 15 to 30 seconds to back up. That’s a nearly two minute time out every fifteen minutes!
And you can’t do anything like “only the active project” either. You may not do it, but I usually do indeed have around four or five projects open at once, and among those I use about three of them on a very regular basis as I transition to different real-world tasks throughout the day. It might have been ten minutes since I last did anything in the other one. E.g. right now I’m typing into this project I use for communications), but the user manual project in the background is what I was working in before taking a break and reading the forums. So does that now not get backed up because it is in the background—for how long, three hours even if I never come back to it? That’s pretty awful too—now you don’t really have a good sense of when anything is backed up, and stuff you only use now and then may never be, until you trigger one of the other conditions.
As Katherine notes, project backups are whole copies (whole copies that are then zipped, which is even slower than duplication), and can sometimes be an awful lot of material. Obviously someone with gigabytes of data in their open projects would likely avoid any kind of timed backup setting like the plague, they probably do not even use the backup on close/open options—but the problem isn’t really in the extremes. Like I say, all it takes is two or three open projects and a total backup time of 15 seconds every 15 minutes to make you really start hating the feature.
I know, I’ve tried it.
I heartily recommend the manual save backup option. That was the answer to the removal of this setting. There was a need for an easy way to make incremental backups throughout the day, and leaving the decision of when to take a 30 second break should be up to you, and you should use it as frequently as you please.
It is better than Save As, and far easier because all you have to do is hit ⌘S and take a sip of water.