Yes, I totally agree on the problem with ending a day before all actions are spent. I make lists of which nichelings to travel with on my phone, and then whoops! Put the phone down on the spacebar, wasting a valuable day of their life!
Yes! This! Several times I have driven my nichelings to slow extinction, or worse, they've died out fast in an environment they haven't been adapted for.
This would be so helpful. I often find I'm racing to breed with an animal as often as possible before it dies, which is frustrating when chance simply doesn't lead to the offspring inheriting what I want. It often happens with immunity genes. A longer life span could give the option of making that less stressful. Or a shorter lifespan could be an extra level of difficulty if you're into that.