Developed RSI and overcame it through learning stenography with Plover. I've used it exclusively (only using the keyboard to login to the computer) for 2 years. I'm a full time developer and it works great. There's a learning curve for a few months before being able to switch to stenography completely. Practice was running drills with a metronome for 15 minutes or so a day, progressing to the next lesson after hitting my target of 70 wpm at 95% accuracy. Comments (generally on this topic) often make it seem harder than it is or raise scares about impracticality. Practice was boring. However, I found that 30 wpm is plenty sufficient to do programming on the job, as thinking takes far more time than putting characters on the screen. Very rarely, at least for me, am I writing continuously for more than a moment. Stenography is a far superior input method than 1:1 character-wise entry. Given my condition, I didn't really have a choice. If keyboard entry works for you, great. If you have RSI or are developing it, learning steno is 1000% worth it. Prejudice against invisible disabilities exists. People dismiss them, judge you, and take advantage of your situation. Stenography is a way out of that. Also, see an occupational therapist (a professional who specializes in repetitive, work-related injuries). Good luck to anyone going through RSI. You're not alone and you will get through it.

Link to Plover to save you (potentially) painful typing: https://www.openstenoproject.org/