ksshooter, I do NOT have any SF lights, but one of the Police Services near me issues its members with 8NX, and those members seem to really like them.
A lot of Units in my Division, including mine, have Streamlight Polystingers issued to the cars, with wired-in charger units.
I used to use the Polystinger in my patrol vehicle as my main duty light, but more often now use my Koehler Brightstar 3 D that I have modified to use 3 x 123A lithium disposables.
I have only had to draw my sidearm about 6 times in 29 years, and a shotgun once; combine that with carrying a S$W 5946 and being under strict policies of no unauthorized weapon modifications, I do not use weapon-mounted tactical lights.
It has only been since coming to this site that I realize the value of back-up lights and how FAR MORE OFTEN I have needed those than I have EVER needed my sidearm, let alone a BUG. I now carry a Pelican M6 xenon and Dorcy Spyder on my duty belt, plus have a Mag-lite 3 C modified to use 3 x 123A lithium disposables in the car.
The use of a rechargeable light as your main duty light IS a good idea, especially if you use the kind that uses power sources that require removing the source from the lighting tool body to then put the source on a charger so you can use one source, charge a 2nd source, then swap. The next best option then is a lighting tool that connects to a charger, so that when you do so, you then have an always-on-the-belt lithium-disposable-power-source back-up lighting tool. The lithium disposable will sit there, waiting to be used, and will have a very slow self-discharge.
Even with the removable power source main light, having at least 1 back-up light with lithium-disposable power source is a good idea just in case - unless you only carry 1 clip of ammo in your duty weapon, and even I carry 2 extra clips.