Going on vacation

I have a pet corn snake. I'm going out of town for 5 days, and I'm concerned about his heat. I use both a hot rock, which stays on 24/7, and a heat lamp, which I turn off at night. Should I leave his lamp on the whole time I'm gone? It gets about 70 degrees in his tank when it's off. I don't want him to get too cold, but I've also heard it can stress snakes out to have light all the time.