Well, after overviewing some episodes, it seems like... all of them are still quite young... I mean, look at Giroro to Garuru. Does Garuru look like an old fart to you?! No! He looks quite... uh, please explain, Samni. XD
Another thing, episode 125 states that even Keroro imagines himself... well he imagine's Kululu taunting him about still ''being a kid.'' (about some sushi thats gross xD) Like I said, when you compare the platoon, it shows that they are still quite young. In so, Keronians have different aging rates.
Again at Giroro and Garuru, would a experienced 42 year old war horse not know some tricks and common knowledge of a pro? Giroro isn't lazy.
My point stated.












