The higher +%brightness you go the shorter the life. +30% last well. I find +50% only last 18 months regular use. +30% have lasted 5 years. I fone bulb blows replace both. Keep the second and use next time one blows to give a matched pair or you m ay find its one then the other blowing add infinitum.
The main reason the lights are poor is that the main beam is too high with the dip set at the optimum. I find running wiht the lights set on 1 improves main beam significantly. Poor light design as you cant change this relationship. Adjustes affect the whole light unit. If you fiddle you will find its not bad lighting but poor aim. Spend time getting the aim optimised, its worth the effort to get best overall performance.