Is it possible to make rice porridge without simmering for 1 hour+?
I make rice porridge in the oven. I bring the rice and milk to a boil on the stove and then place the entire pot, lid on, in the oven on ~90 degrees C for 4-8 hours, depending on the amount of rice. I'm basically using a DIY slow cooker. I imagine there are methods involving an actual slow cooker as well. The total time for my method is longer, but you don't need to stir constantly after bringing it to a boil. 

If you have a pressure cooker, that can be used to make rice pudding much quicker. A pressure cooker recipe will according to my Google-fu take about 30 minutes total, and no stirring.