In my experience, everything sold by Moultrie is of poor quality. How long it lasts, or if it even works when you get it is always going to be a guess.
For my feeder and camera, I first went with a cheaper solar panel, probably a Moultrie, that worked good for a couple of months, but they died on me. I was impressed with the results, but realized I needed better quality. Northern Tool sells some decent solar panels. About ten years ago, I bought one very similar to this one and it's been working great every since. I've replaced the battery 3 times since then, but never any problems with the solar cell.
http://www.northerntool.com/shop/tools/product_200512420_200512420