I'm applying for MHA programs this year and these were all questions I asked myself. My father used to be an administrator for a CHC health system's telecommunications program in the late 90's, and i've spoken with a few other hospital administrators that are family friends so I think I can give generalized answers to your question.
The general consensus is no you don't work as much as most physicians and you have a more predictable schedule. e.g 8-6 seems pretty common and there generally aren't night shifts... although you may work into the evening. 60-80 hour work works are pretty standard. In addition to work, there's a lot of outside meetings, fundraisers, etc. that you are expected to attend so these positions do tend to be fairly demanding.
Admins generally aren't "on call" but with that said, as emergencies arise, you likely will be called in. This is more common in smaller hospitals where administrators essentially are taking on more diverse admin roles.
A lot of these factors are dependent on the type of facility and your exact administrative role. For example, a human resources administrator is much less likely to work non-standard hours than an operations admin.
Hope this helps and/or that some current admins chip in!
