The main thing to think about is that they are a cold blooded creature so they need something to say warm. If they are against your skin they could stay out for a pretty long time. Just don't let them roam around your house, get cold, slither in dust and hair, etc. I can't say what the longest amount of time they could stay out and stay healthy, but if you keep them warm enough I would say they should be fine as long as you want to babysit them.