Okay, I just learned something interesting while surfing YouTube. Turns out that there is a glitch in Monster Rancher 2 DX. This glitch has a very interesting effect. If your monster goes on expeditions, you'll only lose about a week of lifespan despite the fact that your monster is on a month-long expedition. Normally you'd lose the 4 weeks that your out on the expedition plus another week due to fatigue, but this glitch only registers the lost week from fatigue. As a result, if you go on as many expeditions as possible your monster can effectively double its lifespan. Now I'm starting to understand why Mero lasted as long a she did, longer than she was supposed to, as she went on several expeditions, but only lost a week's worth of lifespan on each because of the glitch. Don't tell TECMO this, as they'll patch it, but it's a very interesting discovery and exploit if anyone is playing Monster Rancher 2 DX.