I think it makes sense, but I also think if the detectors are that high off the floor, tenants are less likely to change the batteries when they go bad. 

Hardwired so no batteries to change.

Get a heavy duty Surge Protector and Battery pack combo. 

Some of mine are too lazy and cheap to change the smoke detector batteries.

I have put all battery operated digital locks on my doors and change the combo with each tenant.

I gave them my reasons, the high bills, the no longer being able to feel comfortable at home doing anything, not being able to recharge my batteries in a way, not feeling like it was my home, feeling like a third wheel (which roommate sarcastically replied with "ohhhhh Wow").

Most reviews are saying 1-2 years per set of 4 AA batteries.

There already are several battery ones. 

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Additionally, with the fire risk in my area we experience a significant number of mandatory power outages to mitigate fire risk, so those panels (plus the back up battery) actually added a significant amount of value to my home.