I had two rats, my first one was three days shy of her 6th birthday when she passed away. I have a adorable story with her.
So I was having treatment done for cancer, well just had surgery done. Well Gabby (that was her name) she was trained to be either in her cage or with me in the room, she had a rope toy to use to get onto my bed and down to her cage to go potty. Well we were snuggled together, her in the crook of my neck. Well she got up and went down to her cage, she got a mouth full of her food, set them on my chest and started force feeding me her food. She was actually prying my lips open enough to get the food in, I did not want to make her feel bad so I hid the food under my tongue. I think I did actually eat one of the biscuits though, it actually tasted pretty good. XD
My second one was a male, his name was Oliver 'Buddy' Twist. He lived until he was 4 years old. I had him throughout my second treatment and love to be cuddled, scratched behind the ear and be spoken too.
I raised both rats when they were somewhere between 1 and 3 weeks of age, and they still depended on milk for food, so yeah I was feeding about every 1 to 3 hours day and night. XD