8 hours are too short to sleep on 24 hours are too long and keep you shielded 12 hours would be perfect timing to wake up with enough time get some troop kills and shield up for the night again
I like this idea. I'm always nervous as to when my shield will expire and renewing. It would be nice to be able to put on a 12 hour and wake up after a 10 hour nap without being attacked. 24 hours are quite annoying
You can always give your login to a trusted friend to shield for you if needed, and you can do the same for them.
That's what the majority of big players do. And the ones that don't are the ones that get zeroed.
Otherwise, your entire army is not worth losing for 1,500 gems. Just use the 24hr. Join some monster guilds if you're low