My opinion is; depends on what you're trying to see and how accessible the cameras are going to be? I wouldn't want them low enough to be taken or messed with, but yet getting on a ladder every 30 days to change the batteries would be a pain. IR LED's will use up some battery, depending on how bright they will be and if they can be configured to run low/med/high or during a specific time frame. Auto-switching at dusk might not be the best option for what you're trying to view.

Also do they require lithium batteries? That can be costly. $$ Alkaline batteries don't work well during severe cold either.