It is push on and off. My friend only turns it down all the way until the lights extinguish and never actually turns the switch off. It is push on and off. My friend only turns it down all the way until the lights extinguish and never actually turns the switch off.

The components inside the dimmer, I think the triac, respond different at different temperatures. Keeping it energyzed can cause temperature change inside the dimmer. So common for those dimmers to just get turned down instead of slapping it off. Even when pushing off, the dimmer may be so far back in the wall it doesn't readily shut off. Touch the metal screws holding the plate on, they probably feel warm. People sometimes complain of a smell, I find the dimmer has developed a fishy smell after heating up, I just replace it and done. But that is not common to find the lights back on burning in the morning after shuting them down low to off but never can tell unless it is actually switched off. The components inside the dimmer, I think the triac, respond different at different temperatures. Keeping it energyzed can cause temperature change inside the dimmer. So common for those dimmers to just get turned down instead of slapping it off. Even when pushing off, the dimmer may be so far back in the wall it doesn't readily shut off. Touch the metal screws holding the plate on, they probably feel warm. People sometimes complain of a smell, I find the dimmer has developed a fishy smell after heating up, I just replace it and done. But that is not common to find the lights back on burning in the morning after shuting them down low to off but never can tell unless it is actually switched off.