You should get at least 4 weeks out of the D batteries, and probably longer if you're not set up on bait. If you're just on a trail I'm sure the batteries will last for two months, minimum. Or if you're worried about it, get two external batteries for each camera. Each time you check them you can swap the battery out with a freshly recharged one.
I would recommend you at least buy one. It's well worth the $80. I can't recommend either of the other two you mentioned.
Two others I would recommend right now would be the Moultrie d55 at Rogers Sporting Goods, currently it's on sale for $70. Great camera for the money.
The other would be if you can find a refurbished Moultrie M80 on eBay. They are going for $80.
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