Yea, there's no single answer to this. I've had mine outside for days at a time or for only 30 mins, it depends on how hot it is outside. If he has access to shade he can stay out longer, and you can mist him every little bit to keep him cooler if it's maybe around 80*+ outside. I mist quite a bit if it's over 80* usually. Watch his body language, if he looks like he's overheating or is pacing around like trying to find shade then you can bring him back inside.