Some personal notes on Streamlight and Surefire, which are the only two brands I used and have experience using.
The Surefire X300 series (I've got an old X300, before the "U" models came out; and an X300U). The X300U stopped working and Surefire provided a replacement after evaluating the broken one. I've also had a switch stop working on the X300. Surefire provided a replacement switch under warranty, without having me send back the original switch.
I've got a Streamlight TLR-1 and a couple of TLR-1HL lights. The TLR-1 switch also broke, but Streamlight doesn't have a lifetime warranty as Surefire does. This was ok and understood. A replacement switch was quickly available online should one ever be needed.
Here's an Amazon link should anybody need a TLR-1 switch fairly fast:
shorturl.at/hmuwV
I could actually get a Streamlight TLR-1 switch faster than Surefire can ship a replacement X300 switch under warranty (which might take 3 weeks as I had to email back due to the customer service rep forgetting to send me the replacement after the 1st email).
I found having a spare, when working with a weapon-mounted-light (WML) daily for work, ideal for me. Otherwise, it's inconvenient to switch holsters out on a duty belt, from a WML holster to a non-WML holster, although that's another option. Not everybody will use a WML for daily work and not everyone will experience breakages.