To make it a little easier on people I went ahead and calculated the average lifespan of Monsters in Years/months. I literally trained every single Pure Bred Monster to get these results. Your Assistant always says to retire a good year and a half or less before the actual death date. She even requests it 2 to 3 times. The list goes from shortest lifespan to longest:


Joker: 2 years 9 months
Phoenix: 2 years 9m months
Gali: 3 years 2 months
Naga: 3 years 3 months
Monol: 3 years 4 months
Zan: 3 years 5 months
Dragon: 3 years 5 months
Pixie: 3 years 6 months
Falco: 3 years 6 months
Suezo: 3 years 7 months
Ducken: 3 years 7 months
Tiger: 3 years 7 months
Centaur: 3 years 7 months
Plant: 3 years 9 months
Mocchi: 3 years 9 months
Mew: 3 years 9 months
Hare: 3 years 9 months
ColorPandora: 3 years 9 months
Abyss: 3 years 10 months
Ogyo: 3 years 10 months
Beaklon: 3 years 10 months
Baku: 3 years 11 months
Durahan: 3 years 11 months
Pancho: 4 years 0 months
Piroro: 4 years 1 month
Xenon: 4 year 2 months
Golem: 4 years 3 months
Hengar: 4 years 8 months
Lesion: 4 years 8 months

Now, this is using the "No sleep method" and the "Sleep" for bad stress and before a tournament also. ( For Dragons )