Even the PA mini dots have a 1000 hour battery life. That's something like 40 days of constant on mode.
For most folks in the world that's plenty. I wouldn't mind having a real T-1 just for the battery life of the unit and will probably have one eventually but my PA mini dot gets the job done and has for thousands of rounds.
Glock 17 (Dad's old duty sidearm)
And some other stuff