I was an /r/ kid. Actually, I was a lot more than that, but I had that lingering /r/ after my other sounds were corrected.
When I was little, only my mom could understand me. She took me to speech therapy at the Texas Tech clinic. My best guess is I had blend reduction, final-consonant deletion, or fronting, or a combo. But I only remember working on /r/ in 4th grade, having it "click" during the summer, and not going to speech therapy in 5th grade. Which brings me to...
R went through a few artic developmental stages. She had fronting, blend reduction, /f/ for /th/, and a frontal lisp for a while. Nothing big, nothing that a little modeling didn't correct.
But the /r/ stuck. And I'm an SLP.
One day when she was about 4, I did the unthinkable. I tried to get her to say /er/, even turning her upside down. She just said "uh" and I thought we could try again in a couple of years. Then… that night as she was brushing her teeth, she practiced saying /er/. On her own. And called me in to hear it. She had it! The /r/ took a little more work, but she was using /r/ in all positions in conversation by the end of kindergarten.
Example 2: I inherited an IEP student who was working on fronting. He mastered that by the end of kindergarten. The /r/ stuck. I was young and naive and didn't realize that I could have put him on consult, so we pressed forward with the /r/. He left for Christmas Break during his 2nd-grade year slightly stimulable for /r/ in words and came back using /r/ in all positions in conversation!
Example 3: More recently, I had a very bright student who had several errors that were pretty quickly remediated. Except for the /r/. We worked. We tried everything. During her 4th-grade year, I started seeing her individually after school a couple of days a week to try to fix the /r/ once and for all. The first session, she came in and announced, "I don't know why I'm heuh. My fwiends unduhstand me. I make good gwades. I don't see a weason to change." Still, she worked with me with some but limited progress. A few weeks later, she came and announced, "Okay, let's get to wuhk. I heuh it." She had recorded herself on the iPad doing a play at home and couldn't believe how she sounded. Even though we had used the iPad in therapy…. From then on, it was an easy climb to conversation in just 2 1/2 months' time!
Here is my struggle. What if I worked on /r/ earlier and students didn't have to miss as much class time? What if I'm working with a student who is not ready for /r/ and there's a lot of class time missed? How do I distinguish a developmental /r/ from one that's going to linger?
I once heard Wayne Secord say that SLPs should address /r/ right after fronting because that's hitting all the back sounds. That worked with Example 1 and 2. But my little Example 3 missed a LOT of class in 2nd, 3rd, and half of 4th because she wasn't ready. So how do we know? Without a crystal ball, we don't. I'll keep working on stimulability, readiness skills, and awareness and remembering that each student is an individual. Especially with /r/ sounds.