I know that they are a lot of fans of the deep sleep functionality of the ESP but from my personal experience for a long time running/low power consumtion project this is one of the best approaches.
A related ESP8266 Forum thread where you can see different implementations:
viewtopic.php?f=13&t=5747&start=40
Available on Tindie: https://www.tindie.com/products/nEXT_EVO1/universal-ac-mains-dimmer-mpdmv41/