If your lamp transformer maximum of 40 volts, and then fitted with a 42 volt lights. It's not a problem, it may just not be lit normally. Dangerous and destructive is when the opposite happens, house lamp 42 volts then fitted with 40 volt lighting.
If you use LED light, no need change the lamp often. LED lights have a high energy efficiency, longer life can be up to 50,000 hours, with dimmed adjustable dim and bright.