I have recently installed some 12 volt miniature lights in home. I have them working now but began wondering about how I have the 12 volt transformer wired. The lights are on a switch and I have the transformer in the line before the switch. Thus I have power at the transformer all the time. Is this OK, or should I have the transformer after the switch so that it only receives the high voltage when I turn the lights on?

Thanks for any suggestions.

I would have wired it with the switch before the transformer. On the other hand, your house is likely full of transformers with the 120 V on, furnace, doorbell, the power supplies of your computer and other electronics, all your wall warts, etc. The transformer may actually last better for not being switched on and off.

Somebody that knows code better than I, may say change it.