This is probably one of the most valuable and easy, free pieces of advice.
I worked in the insurance (claims) business for 18 yrs many of which were spent handling workers compensation claims for RSI. All the ergonomic chairs, mice, and other gadgets are fine, but should not substitute for excercize, frequent breaks, and changing up your routine as indicated.
Lastly, I am surprised no one has mentioned chiropractic. This will sound like heresy, especially coming from an ex claims adjuster, but if you can locate a qualified chiropractor who has a PROVEN track record of treating RSI with a focused, fixed period, it might be worth investigating. I had many, many claimants who found success and 100% relief with a particular chiropractor who speciliazed in RSI.
Let the flaming begin