I've shot RMRs for years and...
I'm 62 and have good eyesight, but am prepared for the day the old eyeballs begin to go south. I've shot Bullseye with red dots since 2006 and agree that 3.5MOA is great for that sport. However, many shoot very well with dots over twice that size. On my M&P 45 that I shoot in combat matches I use the 6.5MOA RM02. At 100 yards the dot is only 6.5" across about 1/3 of the width of a man's chest. I have not found any conditions that 6.5MOA has not been adequate to the task.
Now to adjustable vs nonadjustable. The RM01 and RM02 are non adjustable, but do have an internal switch that automatically adjusts the intensity of the dot depending on ambient light. In my experience this is the best set up for a carry weapon and a competition weapon. The Ultra Dot on my 22 is manually adjustable and from time to time the lighting changes so quickly that I can't keep up with it. The RM01/02 never has this problem. Others that use the dual setup or the manually adjustable ones are happy with their choices but for me the RM01/02 is the best setup.
Finally, battery life. The RMR battery on my Bullseye gun is 5 years old and is still going strong. The RMR battery on my M&P is 3 years old and is still strong. If I carried the M&P on a daily basis I'd change annually but since I don't yet, why bother.
Keith