Twist-lock biners are standard tools in all types of climbing and mountaineering. You seem to have gotten the impression that there's something unsafe about them, but that's just not true. In my experience, self-locking biners are strictly a thing that you see on permanently installed setups in a climbing gym. I have never seen one outdoors. When you use a normal twist-lock biner, you just build careful habits so that every time you use it, you're using it correctly. I was taught to get in the habit of locking it when I put it on my rack, so that's just totally automatic. Whenever I finish setting up a belay or an anchor, I click the gates to make sure they're locked.
For multipitch trad I carry four. I always want at least three, for the following purposes:
- One for tying in to the anchor. (They're standard for this use. I have never seen anyone use anything else.)
- Two for setting up an ATC Guide to belay a follower in auto-blocking mode.
The fourth one I sometimes use when leading if there's a particular piece of pro that I want to clip the rope to and make sure it can't possibly come out. However, you can accomplish the same thing with two non-locking biners, opposite and opposed.
Sometimes when building a trad anchor, if I perceive a particular piece as being particularly important, I'll use a locker on it, but again you can accomplish this with two nonlockers.
If you've spent any time practicing self-rescue skills such as escaping the belay and ascending the rope, you'll realize that these can also eat up locking biners.
I don't do other styles of climbing very much, but for example a common way of setting up a bombproof toprope anchor for a bunch of boy scouts to climb on all afternoon would involve roughly five locking biners. Say you have two bolts, so you put two lockers in there. Then you have the master point of the anchor, and you put three locking biners in there for the toprope to run through. If you look at standard technical manuals for single-pitch, they recommend the multiple biners in order to cut down on friction, as well as for increased redundancy. If you take a class such as the AMGA single-pitch instructor (SPI) class, this is the technique they teach for people training to be guides. (I think most guides use steel biners for this purpose because they don't wear down as fast.)
Here in North America, the standard textbook on this sort of thing is Long and Gaines, Climbing Anchors. For the AMGA SPI class, the text we used was Gaines and Martin, Rock Climbing: The AMGA Single Pitch Manual.
