Digimon World

Hi, I wonder if anyone else is playign this game. It is very frustrating. I am having a lot of trouble getting an Ultimate digimon:

-My Diigmon keeps on dying, even if I keep his happinesss level at max, and let him rest a lot to releive his tiredness. How can I prevent this?

-What exactly is 360 hours? Cause it says it takes 360 hours to get Vademon if you do nothing, so would that count as 15 days? Would that be 15 days of his life, or 15 days after being a Champioon?

-Should I bother getting ultimate digimon? I kept trying and read the faqs and its impossible. It takes a lot of time