I'm considering a policy regarding email/text, specifically what times are off limits to contact folks to ensure work/life balance. Thoughts?

Its a good plan. Emails have a tendency to take over your life, if you allow them. I would definitely create "no email hours" or even some "no email days." You will find your life will be easier and that life will not end if you don't respond immediately to every email.

On one hand I consider military leadership as a calling not just a job. On the other, is the sincere concern for life/work balance for the Citizen Soldiers in the Reserve Component. My daughter is a Navy Reserve Nurse Corps Unit OIC. She has command responsibilities and authority. She gets e-mails and texts all the time and at any time from the officers and sailors in her detachment. It seems like a bit much. Here's some ideas you might consider.
-Communication downward at any time, but seniors should use good judgement with regard to non-operational issues and try to communicate so the message arrives between 0700 and 2200.
-Communication upward limited except in emergency to only the next level above the sender and timed to arrive between 0700 and 2200.
-Stress good e-mail discipline. Send messages to the minimum number of people necessary. When e-mailing up-channel only include the authority that issued the tasker and any intermediate level of the organization that may have been excluded from tasking, don't include your boss's boss. When e-mailing down-channel, only include action addressees and copy to those required to coordinate. In other words, cc addressing the entire unit is a waste of time for everybody.
-To maximum extent practical, seniors should allow subordinates 2/3 of available time to respond to taskings.
-Analyze the battle rhythm of the unit and identify days when communication traffic is low. Designate a few of those days each month for emergency communication only.
-Discuss the idea of limited communications hours or days with the senior NCOs. They will have a good perspective on the practicality of the initiative and how it might be implemented.

I think it's a good idea, of course, there are times when such communication needs to be done even on the weekends. Work/Life balance is super critical. I know there are days I'll put my phone on Do Not Disturb and only allow certain numbers to contact me during those times.