I wondered about Satan's longevity myself.
No doubt the manner in which God created angels is8 different than the way he created humans. I do not believe angels have energy that comes from within. Much like oursleves they must take something in (food, or some other energy creating source) to be sustained; otherwise, they would be immortal, like the 144,000's club.
Satan and his demons actually require destruction, no doubt from beings stronger than themselves or by ones given the authority to do so.
I don't believe the angels have free reign to enter God's presence either (to come and go as they please). -I mean what if God is using the throne. I believe there is some kind of protocol.
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Another question that has perplexed me, is why did God take so long to create us? -I guess the starting point really doesn't matter then does it? -think about it.