Heat is something I will be concerned with when I get to lighting up mine.   Hopefully pretty soon!   One thing that I have heard from more than one person who lights up their models.   Anything with a lot of LED's is not left on for more than 15 minutes.   Once you get yours done, I would turn it on and just check up on it ever few minutes checking for heat.   Once it is warm to the touch, turn it off.   You will then know how long you can leave it on. 

I am going to use two LED light strips in mine and those put out quite a bit of heat.   So I won't be able to leave mine on for long either....