Been riding for 34 years, turn signals and all gauges are the first to be removed.

Sure, you can do without the speedometer. But there are many more valid reasons for keeping it, than there are for getting rid of it.
I'd say your mechanic was spot on........I wouldn't advise it sounds like good advice from a mechanic.
But as said, you can do without it, you just have a few more inconveniences to deal with.

Not sure on the bikes, but you are half correct when it comes to newer 4 wheeled vehicles. The PCM keeps that info, but the cluster always keeps it. Like on many or all newer cars and trucks if you were to buy a used cluster and plug it in to your car the cluster will read the mileage that was last on it-not what your PCM says unless it's reprogramed to read what the PCM has stored. This goes for digital odometers too.

I don't care for the speeding tickets. I need to know how fast I'm going.

I have done the exact same but I want to keep the indicator lights. My speedo has 4 wires coming form the main harness, one is black, which I assume needs grounded, which other wire did you ground. Is amazing there are not 100 posts about guys doing same. See my post here https://www.hdforums.com/forum/sport...tor-panel.html. Thanks for any asist. Robert M.