Replace in-series incandescent lamps in a makeup mirror with LEDs
Probably worse If the LEDs are only DC,  and just as bad if AC in series which is non-linear.

Now the 4W lights probably are enclosed so they get hotter and reduce life from 3000h by 50% for every 10’C rise above open ambient. A Triac dimmer could solve that as well as a tiny low speed fan.  You could use 12V stripLED cut down to size and powered by 12Vdc 1A