If, at every 105K miles, the spark plugs will be removed for replacement and the valve covers will be removed for the recommended valve clearance check/adjustment, that would seem to be a convenient opportunity to also clean the valves, if needed.I'm not one for fearmongering, but if your intention is to drive your 3rd gen for 200k miles +, I'd plan for some valve cleaning. Is it a benefit? Yes. I think that's what the OP is trying to find out, plus wants a recommendation of what to use.
I think a walnut blasting at 100k would be great if valves were caked.