I've got "experienced" Shimano and Son dyno hubs, with about 40,000 and 20,000 miles on them. Haven't need to service either (knock on wood) so far.

Although I was a bike commuter until Covid, I developed a distaste for batteries similar to O.P.'s. Although I had a couple supplemental battery powered blinkies on each bike, the dyno lights were the ones I was pretty sure were working every night or morning.

Time to ride? No need to worry about whether or when the batteries were charged. Just go to the garage, pull out a bike, check the tires, and ride away!