Where are they mounted and are you using mudguards?
In over two years of daily commuting in all weathers, ALL my original lights are still going strong
I use guards and position them where they’ll get wet from rain, but not in a spray of water. My bike lights on both my MTBs are also fine, same as my brompton. In fact, now I think about it, I’ve never killed a rear light. I realise I’m now tempting fate
Commuter is on pannier stay (like the seat stay but more vertical) and mounted at the back of the rack. Another at the back of my rack pack, and another on the back of my lid
MTB have them mounted on the seat stays – PDW something and an Aldi something
Brompton has an Alpkit Tau on the back of the seat