@Shawn
I have been using kettlebells since 2001 (I am currently 52 years old).
I have never injured myself lifting kettlebells with the following exceptions:
--Bruised forearms learning to snatch. Of course snatching was the first thing I tried to do with my new kettlebells when I first started. I had the original RKC book/video, but had no idea what I was doing. I just banged the hell out of my forearms until I figured out how to avoid it, mainly by trial and error.
--Occasional torn skin on hands, especially early on.
--Pulled a QL muscle carelessly picking up a KB after my wife yelled at me to move it.
--Occasional flare ups of elbow tendinitis, especially when first learning the clean and snatch. Was also doing a lot of heavy pull ups, and it tends to still flare up if I overdo it on the pull ups (Dan John calls this MAPS -- Middle Aged Pull Up Syndrome).
--The only other training injury I can recall is when I dumped a barbell squat forward onto the rack pins many years ago and developed some sciatic pain.
Now, I do have a long list of sports injuries: I have grade 4 arthritis is my knees and ankles, I've had two shoulder surgeries and one knee surgery, broken bones in ankles and fingers, broken noses (that is, one nose, broken multiple times), broken ribs, torn ligaments in fingers, innumerable sprained ankles, pulled muscles, etc. But all of these were acute injuries suffered playing sports or arthritis related to wear and tear of playing sports.
Is it possible that things I did in my training contributed to some of these acute injuries? Maybe, but there is no way to know that.
My retrospective advice on training longevity:
--Be patient. Trust the process, punch the clock and do the work. Let the progress happen naturally. Don't be afraid to challenge yourself, but don't make it the focus of your training or feel pressure to progress at a certain pace. This also goes for doing specific exercises -- develop competency in your form before charging ahead with volume and load.
--Don't neglect mobility. Do some kind of movement exploration that gets you moving in a variety of novel ways that supplement/complement your main training. Losing movement flexibility (in the figurative sense of being able to move freely in lots of ways, but also the literal sense of range of motion) sneaks up on you as you get older. To quote Ernest Hemingway, it happens two ways, gradually and then suddenly. Start working to maintain it before you have to start working to restore it.