Hi segler. Speed genie is designed so that you can see the result after each run, for speed set it between you're downwind and upwind speed. For alphas set it below you're min gybe speed.
Here's my set up. I'm not sure about needing logging on just for the display, but it won't hurt to have it on. Every thing else there does affect the display.
If you want a permanent display of current speed, then set "speed genie" to a low number, I think it will display current speed once you exceed that number, it will also display whatever you've set up at the end of session.
But remember "max speed" is really max speed + noise. if you want to be more accurate you need to average it out a bit. setting AVG MSEC to 1 will give a 1 second average. You'll notice I've turned MAX off by putting an X alongside it. It's just too misleading.
Where there is a "TOP" alongside the result it shows a split field with best since last reset and last run.
There is a spec somewhere of watch battery life but with permanent display I don't think it's all that long. I'll take a huge guess and say about a week,