Someone else commented that their impression was that the making tens stuff comes and goes relatively quickly in Singapore math as students learn their addition facts.
I have a couple of comments: first, to take off on what CassyT says, we are handicapped by our length of living. It may seem to the adult whose child has grown that this making tens stuff goes relatively quickly as their mathematical competence comes in. But that isn't true in the time frame of grade 1.
By the end of grade 1, PM has kids doing mental math to 100, so yes,big picture, the specific strategy of making tens doesn't last long. But to the first grader, it's what they do for nearly all year, constantly, repeatedly, and for weeks on end. Successful mastery of it will make the learning of addition and subtraction facts much easier, and students who have committed the answers to memory don't rely on them anymore. That process takes thousands of examples for many children.
Second comment: most people here used Singapore math primarily as a home or after-schooler. Often, the parent was mathematically talented and often, so was the student. Few of these people saw or read in detail about the pedagogy used in PM. Almost none *did* the main portion of that pedagogy: the concrete portion, skipping often to the textbook almost immediately. I will speak more about this in another post.
Here's the outline of the unit showing the prevalence of Making Tens: