I have been scouring the guide for various actions and their effects on your monster's lifespan. I haven't come up with much, but found 1 good thing.

Tournaments have an effect on your lifespan. The better you finish, the lower the effect. (Winning the tourney has the lowest effect). The same is also true Fatigue and Stress. The higher you finish, the less you add to fatigue. The higher you finish, the lower your stress level too. (For stress, it uses the word Recover. If you finish high, your stress is actually lowered.)

The one line in the chart I can be sure of is the top one-

Championship	Fatigue Up a little	Stress Recovered a lot	Lifespan reduced a little
?	Fatigue Up some	Stress Recovered some	Lifespan reduced some
?	Fatigue Up a lot	Stress Recovered a little	Lifespan reduced a lot

If anyone finds information on other things that definitely reduce lifespan (besides items) then please post here.

Is it possible that the second and third boxes refer to placing
second and last place in a tourney?

They are related to how you do,for sure. But, there is another chart that explains money gained where you finish and the same indicators aren't present.

I am thinking that the second one is "Finish tourney" and the third one is "withdraw". I have to spend time with the kanji...

This is huge. Thanks.

No wonder my Pooch hit old age early. It placed low
on the tournament level about three times.

Knowing this I will hold off from entering any tournement I am not certain that I will win.